diff --git a/doc/index.html b/doc/index.html
index 3cabf5e..e884096 100644
--- a/doc/index.html
+++ b/doc/index.html
@@ -529,11 +529,12 @@ data-styled.g140[id="sc-global-kJtbWf1"]{content:"sc-global-kJtbWf1,"}/*!sc*/
 </div></div></div></td></tr><tr><td class="sc-fzqBZW sc-fzoyAV sc-fzokvW ilQYAU" kind="field" title="ccs"><span class="sc-fzoXzr jYkWkg"></span><button aria-label="expand properties">ccs<svg class="sc-fznKkj czpFYH" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg></button></td><td class="sc-fzoLag fNYEXC"><div><div><span class="sc-fzqzlV sc-fzqLLg ghLFqa">Array of </span><span class="sc-fzqzlV sc-fzoxnE iMySHJ">objects</span><span class="sc-fzqzlV sc-fzoMdx klHALA"> (<!-- -->Recipient<!-- -->) </span></div> <div><div class="sc-fzoant sc-fzoYHE eTVXpd"><p>Array of <code>Recipient</code> objects to be used as &quot;CC:&quot; addresses for the email</p>
 </div></div></div></td></tr><tr><td class="sc-fzqBZW sc-fzoyAV sc-fzokvW ilQYAU" kind="field" title="bccs"><span class="sc-fzoXzr jYkWkg"></span><button aria-label="expand properties">bccs<svg class="sc-fznKkj czpFYH" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg></button></td><td class="sc-fzoLag fNYEXC"><div><div><span class="sc-fzqzlV sc-fzqLLg ghLFqa">Array of </span><span class="sc-fzqzlV sc-fzoxnE iMySHJ">objects</span><span class="sc-fzqzlV sc-fzoMdx klHALA"> (<!-- -->Recipient<!-- -->) </span></div> <div><div class="sc-fzoant sc-fzoYHE eTVXpd"><p>Array of <code>Recipient</code> objects to be used as &quot;BCC:&quot; addresses for the email</p>
 </div></div></div></td></tr><tr><td class="sc-fzqBZW sc-fzoyAV sc-fzokvW ilQYAU" kind="field" title="attachments"><span class="sc-fzoXzr jYkWkg"></span><button aria-label="expand properties">attachments<svg class="sc-fznKkj czpFYH" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg></button></td><td class="sc-fzoLag fNYEXC"><div><div><span class="sc-fzqzlV sc-fzqLLg ghLFqa">Array of </span><span class="sc-fzqzlV sc-fzoxnE iMySHJ">objects</span><span class="sc-fzqzlV sc-fzoMdx klHALA"> (<!-- -->Attachment<!-- -->) </span></div> <div><div class="sc-fzoant sc-fzoYHE eTVXpd"><p>Array of <code>Attachment</code> objects to be attached to the email</p>
+</div></div></div></td></tr><tr><td class="sc-fzqBZW sc-fzoyAV sc-fzokvW ilQYAU" kind="field" title="placeholders"><span class="sc-fzoXzr jYkWkg"></span><button aria-label="expand properties">placeholders<svg class="sc-fznKkj czpFYH" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg></button></td><td class="sc-fzoLag fNYEXC"><div><div><span class="sc-fzqzlV sc-fzqLLg ghLFqa">Array of </span><span class="sc-fzqzlV sc-fzoxnE iMySHJ">objects</span><span class="sc-fzqzlV sc-fzoMdx klHALA"> (<!-- -->Placeholder<!-- -->) </span></div> <div><div class="sc-fzoant sc-fzoYHE eTVXpd"><p>Array of <code>Placeholder</code> objects. Any occurrences of <code>{PLACEHOLDER_NAME}</code> (<code>name</code> in all caps enclosed with curly brackets) in the email&#39;s HTML or plain text will be replaced by <code>value</code>.</p>
 </div></div></div></td></tr><tr class="last undefined"><td class="sc-fzqBZW sc-fzoyAV ewSDWh" kind="field" title="key"><span class="sc-fzoXzr jYkWkg"></span>key</td><td class="sc-fzoLag fNYEXC"><div><div><span class="sc-fzqzlV sc-fzqLLg ghLFqa"></span><span class="sc-fzqzlV sc-fzoxnE iMySHJ">string</span></div> <div><div class="sc-fzoant sc-fzoYHE eTVXpd"><p>API key to authenticate request with</p>
 </div></div></div></td></tr></tbody></table><div><h3 class="sc-pbIaG kfpsaT">Responses</h3><div><button class="sc-pJurq eyfSne"><svg class="sc-fznKkj fscamO" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg><strong>200<!-- --> </strong><span class="sc-fzpkqZ ebKPJY"><p>The request was received and processed.</p>
-</span></button></div></div></div><div class="sc-AxgMl sc-AxheI hkIgFQ"><div class="sc-oTbqq fJLoZr"><button class="sc-pjSSY ewatGX"><span type="post" class="sc-prOVx hObpXE http-verb post">post</span><span class="sc-paXsP bhaFYt">/sender.php</span><svg class="sc-fznKkj ejwrda" style="margin-right:-25px" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg></button><div aria-hidden="true" class="sc-qQmou laHEoQ"><div class="sc-qYiqT kPAzCv"><div class="sc-fzoant sc-fzoYHE eTVXpd"></div><div tabindex="0" role="button"><div class="sc-pAZqv cGlHkj"><span>https://expmail.kumi.live</span>/sender.php</div></div></div></div></div><div><h3 class="sc-fzpans lerNRm"> Request samples </h3><div class="sc-fznzOf jLdbSQ" data-tabs="true"><ul class="react-tabs__tab-list" role="tablist"><li class="react-tabs__tab react-tabs__tab--selected" role="tab" id="react-tabs-0" aria-selected="true" aria-disabled="false" aria-controls="react-tabs-1" tabindex="0">Payload</li></ul><div class="react-tabs__tab-panel react-tabs__tab-panel--selected" role="tabpanel" id="react-tabs-1" aria-labelledby="react-tabs-0"><div><div class="sc-fzpisO dBHtDj"><span class="sc-fzoVTD kNWQuy">Content type</span><div class="sc-fzoJus ixzWHz">application/json</div></div><div class="sc-fznXWL iZtsQe"><div class="sc-fzqMdD cDvkPr"><div class="sc-fzomME ldXyaM"><button><div class="sc-fznAgC jKdGWZ">Copy</div></button><button> Expand all </button><button> Collapse all </button></div><div class="sc-fzoant gGXDRA sc-fzowVh iKXZfK"><div class="redoc-json"><code><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable "><span class="property token string">"subject"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"html"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"htmlurl"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"text"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"texturl"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"recipients"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"email"</span>: <span class="token string">&quot;user@example.com&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"ccs"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"email"</span>: <span class="token string">&quot;user@example.com&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"bccs"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"email"</span>: <span class="token string">&quot;user@example.com&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"attachments"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"url"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"filename"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"key"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></code></div></div></div></div></div></div></div></div><div><h3 class="sc-fzpans lerNRm"> Response samples </h3><div class="sc-fznzOf jLdbSQ" data-tabs="true"><ul class="react-tabs__tab-list" role="tablist"><li class="tab-success react-tabs__tab--selected" role="tab" id="react-tabs-2" aria-selected="true" aria-disabled="false" aria-controls="react-tabs-3" tabindex="0">200</li></ul><div class="react-tabs__tab-panel react-tabs__tab-panel--selected" role="tabpanel" id="react-tabs-3" aria-labelledby="react-tabs-2"><div><div class="sc-fzpisO dBHtDj"><span class="sc-fzoVTD kNWQuy">Content type</span><div class="sc-fzoJus ixzWHz">application/json</div></div><div class="sc-fznXWL iZtsQe"><div class="sc-fzqMdD cDvkPr"><div class="sc-fzomME ldXyaM"><button><div class="sc-fznAgC jKdGWZ">Copy</div></button><button> Expand all </button><button> Collapse all </button></div><div class="sc-fzoant gGXDRA sc-fzowVh iKXZfK"><div class="redoc-json"><code><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable "><span class="property token string">"status"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"error"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></code></div></div></div></div></div></div></div></div></div></div></div></div><div class="sc-oTNDV izusvA"></div></div></div>
+</span></button></div></div></div><div class="sc-AxgMl sc-AxheI hkIgFQ"><div class="sc-oTbqq fJLoZr"><button class="sc-pjSSY ewatGX"><span type="post" class="sc-prOVx hObpXE http-verb post">post</span><span class="sc-paXsP bhaFYt">/sender.php</span><svg class="sc-fznKkj ejwrda" style="margin-right:-25px" version="1.1" viewBox="0 0 24 24" x="0" xmlns="http://www.w3.org/2000/svg" y="0" aria-hidden="true"><polygon points="17.3 8.3 12 13.6 6.7 8.3 5.3 9.7 12 16.4 18.7 9.7 "></polygon></svg></button><div aria-hidden="true" class="sc-qQmou laHEoQ"><div class="sc-qYiqT kPAzCv"><div class="sc-fzoant sc-fzoYHE eTVXpd"></div><div tabindex="0" role="button"><div class="sc-pAZqv cGlHkj"><span>https://expmail.kumi.live</span>/sender.php</div></div></div></div></div><div><h3 class="sc-fzpans lerNRm"> Request samples </h3><div class="sc-fznzOf jLdbSQ" data-tabs="true"><ul class="react-tabs__tab-list" role="tablist"><li class="react-tabs__tab react-tabs__tab--selected" role="tab" id="react-tabs-0" aria-selected="true" aria-disabled="false" aria-controls="react-tabs-1" tabindex="0">Payload</li></ul><div class="react-tabs__tab-panel react-tabs__tab-panel--selected" role="tabpanel" id="react-tabs-1" aria-labelledby="react-tabs-0"><div><div class="sc-fzpisO dBHtDj"><span class="sc-fzoVTD kNWQuy">Content type</span><div class="sc-fzoJus ixzWHz">application/json</div></div><div class="sc-fznXWL iZtsQe"><div class="sc-fzqMdD cDvkPr"><div class="sc-fzomME ldXyaM"><button><div class="sc-fznAgC jKdGWZ">Copy</div></button><button> Expand all </button><button> Collapse all </button></div><div class="sc-fzoant gGXDRA sc-fzowVh iKXZfK"><div class="redoc-json"><code><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable "><span class="property token string">"subject"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"html"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"htmlurl"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"text"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"texturl"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"recipients"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"email"</span>: <span class="token string">&quot;user@example.com&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"ccs"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"email"</span>: <span class="token string">&quot;user@example.com&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"bccs"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"email"</span>: <span class="token string">&quot;user@example.com&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"attachments"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"url"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"filename"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"placeholders"</span>: <div class="collapser"></div><span class="token punctuation">[</span><span class="ellipsis"></span><ul class="array collapsible"><li><div class="hoverable collapsed"><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable collapsed"><span class="property token string">"name"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable collapsed"><span class="property token string">"value"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></div></li></ul><span class="token punctuation">]</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"key"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></code></div></div></div></div></div></div></div></div><div><h3 class="sc-fzpans lerNRm"> Response samples </h3><div class="sc-fznzOf jLdbSQ" data-tabs="true"><ul class="react-tabs__tab-list" role="tablist"><li class="tab-success react-tabs__tab--selected" role="tab" id="react-tabs-2" aria-selected="true" aria-disabled="false" aria-controls="react-tabs-3" tabindex="0">200</li></ul><div class="react-tabs__tab-panel react-tabs__tab-panel--selected" role="tabpanel" id="react-tabs-3" aria-labelledby="react-tabs-2"><div><div class="sc-fzpisO dBHtDj"><span class="sc-fzoVTD kNWQuy">Content type</span><div class="sc-fzoJus ixzWHz">application/json</div></div><div class="sc-fznXWL iZtsQe"><div class="sc-fzqMdD cDvkPr"><div class="sc-fzomME ldXyaM"><button><div class="sc-fznAgC jKdGWZ">Copy</div></button><button> Expand all </button><button> Collapse all </button></div><div class="sc-fzoant gGXDRA sc-fzowVh iKXZfK"><div class="redoc-json"><code><div class="collapser"></div><span class="token punctuation">{</span><span class="ellipsis"></span><ul class="obj collapsible"><li><div class="hoverable "><span class="property token string">"status"</span>: <span class="token string">&quot;string&quot;</span><span class="token punctuation">,</span></div></li><li><div class="hoverable "><span class="property token string">"error"</span>: <span class="token string">&quot;string&quot;</span></div></li></ul><span class="token punctuation">}</span></code></div></div></div></div></div></div></div></div></div></div></div></div><div class="sc-oTNDV izusvA"></div></div></div>
     <script>
-    const __redoc_state = {"menu":{"activeItemIdx":-1},"spec":{"data":{"openapi":"3.0.0","info":{"description":"A simple endpoint to send email messages","version":"0.1","title":"EXPMail","contact":{"email":"support@kumi.systems"}},"tags":[{"name":"sending","description":"Sending out an email"}],"paths":{"/sender.php":{"post":{"tags":["sending"],"summary":"Send out an email","operationId":"sendMail","requestBody":{"content":{"application/json":{"schema":{"$ref":"#/components/schemas/Mail"}}},"description":"JSON defining the email message to be sent","required":true},"responses":{"200":{"description":"The request was received and processed.","content":{"application/json":{"schema":{"type":"object","properties":{"status":{"type":"string","description":"\"Success\" if message was successfully sent, else \"error\""},"error":{"type":"string","description":"Error message, only included if an error has occurred"}}}}}}}}}},"servers":[{"url":"https://expmail.kumi.live"}],"components":{"schemas":{"Attachment":{"type":"object","properties":{"url":{"type":"string","format":"url","description":"URL from where to fetch the file to attach"},"filename":{"type":"string","description":"File name to use for email attachment. If not set, defaults to name from Content-Disposition header of URL if it exists, else the base name of the URL."}}},"Recipient":{"type":"object","properties":{"email":{"type":"string","format":"email","description":"Email address of the recipient"},"name":{"type":"string","description":"Name of the recipient"}}},"Mail":{"type":"object","properties":{"subject":{"type":"string","description":"Subject of the email"},"html":{"type":"string","description":"String containing the HTML content of the email. Takes precedence over `htmlurl` if provided. If both `html` and `text` or `texturl` are provided, will create a multi-part MIME message."},"htmlurl":{"type":"string","description":"String containing the URL to a file containing the HTML content of the email. Ignored (but still validated) if `html` if provided. If both `htmlurl` and `text` or `texturl` are provided, will create a multi-part MIME message."},"text":{"type":"string","description":"String containing the plain text content of the email. Takes precedence over `texturl` if provided. If both `text` and `html` or `htmlurl` are provided, will create a multi-part MIME message."},"texturl":{"type":"string","description":"String containing the URL to a file containing the plain text content of the email. Ignored (but still validated) if `text` is provided. If both `texturl` and `html` or `htmlurl` are provided, will create a multi-part MIME message."},"recipients":{"type":"array","description":"Array of `Recipient` objects to be used as \"To:\" addresses for the email","items":{"$ref":"#/components/schemas/Recipient"}},"ccs":{"type":"array","description":"Array of `Recipient` objects to be used as \"CC:\" addresses for the email","items":{"$ref":"#/components/schemas/Recipient"}},"bccs":{"type":"array","description":"Array of `Recipient` objects to be used as \"BCC:\" addresses for the email","items":{"$ref":"#/components/schemas/Recipient"}},"attachments":{"type":"array","description":"Array of `Attachment` objects to be attached to the email","items":{"$ref":"#/components/schemas/Attachment"}},"key":{"type":"string","description":"API key to authenticate request with"}}}}}}},"searchIndex":{"store":["tag/sending","operation/sendMail"],"index":{"version":"2.3.8","fields":["title","description"],"fieldVectors":[["title/0",[0,0.168]],["description/0",[0,0.095,1,0.129,2,0.129]],["title/1",[0,0.111,1,0.151,2,0.151]],["description/1",[]]],"invertedIndex":[["email",{"_index":2,"title":{"1":{}},"description":{"0":{}}}],["out",{"_index":1,"title":{"1":{}},"description":{"0":{}}}],["send",{"_index":0,"title":{"0":{},"1":{}},"description":{"0":{}}}]],"pipeline":[]}},"options":{}};
+    const __redoc_state = {"menu":{"activeItemIdx":-1},"spec":{"data":{"openapi":"3.0.0","info":{"description":"A simple endpoint to send email messages","version":"0.1","title":"EXPMail","contact":{"email":"support@kumi.systems"}},"tags":[{"name":"sending","description":"Sending out an email"}],"paths":{"/sender.php":{"post":{"tags":["sending"],"summary":"Send out an email","operationId":"sendMail","requestBody":{"content":{"application/json":{"schema":{"$ref":"#/components/schemas/Mail"}}},"description":"JSON defining the email message to be sent","required":true},"responses":{"200":{"description":"The request was received and processed.","content":{"application/json":{"schema":{"type":"object","properties":{"status":{"type":"string","description":"\"Success\" if message was successfully sent, else \"error\""},"error":{"type":"string","description":"Error message, only included if an error has occurred"}}}}}}}}}},"servers":[{"url":"https://expmail.kumi.live"}],"components":{"schemas":{"Placeholder":{"type":"object","properties":{"name":{"type":"string","description":"Name of the placeholder - will be converted to ALL CAPS by the server if it isn't already"},"value":{"type":"string","description":"Value to insert into placeholder"}}},"Attachment":{"type":"object","properties":{"url":{"type":"string","format":"url","description":"URL from where to fetch the file to attach"},"filename":{"type":"string","description":"File name to use for email attachment. If not set, defaults to name from Content-Disposition header of URL if it exists, else the base name of the URL."}}},"Recipient":{"type":"object","properties":{"email":{"type":"string","format":"email","description":"Email address of the recipient"},"name":{"type":"string","description":"Name of the recipient"}}},"Mail":{"type":"object","properties":{"subject":{"type":"string","description":"Subject of the email"},"html":{"type":"string","description":"String containing the HTML content of the email. Takes precedence over `htmlurl` if provided. If both `html` and `text` or `texturl` are provided, will create a multi-part MIME message."},"htmlurl":{"type":"string","description":"String containing the URL to a file containing the HTML content of the email. Ignored (but still validated) if `html` if provided. If both `htmlurl` and `text` or `texturl` are provided, will create a multi-part MIME message."},"text":{"type":"string","description":"String containing the plain text content of the email. Takes precedence over `texturl` if provided. If both `text` and `html` or `htmlurl` are provided, will create a multi-part MIME message."},"texturl":{"type":"string","description":"String containing the URL to a file containing the plain text content of the email. Ignored (but still validated) if `text` is provided. If both `texturl` and `html` or `htmlurl` are provided, will create a multi-part MIME message."},"recipients":{"type":"array","description":"Array of `Recipient` objects to be used as \"To:\" addresses for the email","items":{"$ref":"#/components/schemas/Recipient"}},"ccs":{"type":"array","description":"Array of `Recipient` objects to be used as \"CC:\" addresses for the email","items":{"$ref":"#/components/schemas/Recipient"}},"bccs":{"type":"array","description":"Array of `Recipient` objects to be used as \"BCC:\" addresses for the email","items":{"$ref":"#/components/schemas/Recipient"}},"attachments":{"type":"array","description":"Array of `Attachment` objects to be attached to the email","items":{"$ref":"#/components/schemas/Attachment"}},"placeholders":{"type":"array","description":"Array of `Placeholder` objects. Any occurrences of `{PLACEHOLDER_NAME}` (`name` in all caps enclosed with curly brackets) in the email's HTML or plain text will be replaced by `value`.","items":{"$ref":"#/components/schemas/Placeholder"}},"key":{"type":"string","description":"API key to authenticate request with"}}}}}}},"searchIndex":{"store":["tag/sending","operation/sendMail"],"index":{"version":"2.3.8","fields":["title","description"],"fieldVectors":[["title/0",[0,0.168]],["description/0",[0,0.095,1,0.129,2,0.129]],["title/1",[0,0.111,1,0.151,2,0.151]],["description/1",[]]],"invertedIndex":[["email",{"_index":2,"title":{"1":{}},"description":{"0":{}}}],["out",{"_index":1,"title":{"1":{}},"description":{"0":{}}}],["send",{"_index":0,"title":{"0":{},"1":{}},"description":{"0":{}}}]],"pipeline":[]}},"options":{}};
 
     var container = document.getElementById('redoc');
     Redoc.hydrate(__redoc_state, container);;
diff --git a/doc/swagger.json b/doc/swagger.json
index ba398a9..356c0f3 100644
--- a/doc/swagger.json
+++ b/doc/swagger.json
@@ -44,6 +44,17 @@ paths:
                 description: "Error message, only included if an error has occurred"
                 required: false
 definitions:
+  Placeholder:
+    type: "object"
+    properties:
+      name:
+        type: "string"
+        required: true
+        description: "Name of the placeholder - will be converted to ALL CAPS by the server if it isn't already"
+      value:
+        type: "string"
+        required: false
+        description: "Value to insert into placeholder"
   Attachment:
     type: "object"
     properties:
@@ -107,6 +118,11 @@ definitions:
         description: "Array of `Attachment` objects to be attached to the email"
         items:
           $ref: "#/definitions/Attachment"
+      placeholders:
+        type: "array"
+        description: "Array of `Placeholder` objects. Any occurrences of `{PLACEHOLDER_NAME}` (`name` in all caps enclosed with curly brackets) in the email's HTML or plain text will be replaced by `value`."
+        items:
+          $ref: "#/definitions/Placeholder"
       key:
         type: "string"
         description: "API key to authenticate request with"
diff --git a/sender.php b/sender.php
index c2dc76a..36de3ec 100644
--- a/sender.php
+++ b/sender.php
@@ -22,6 +22,11 @@ try {
     $html = ($json["html"] ? $json["html"] : ($json["htmlurl"] ? file_get_contents($json["htmlurl"]) : null));
     $text = ($json["text"] ? $json["text"] : ($json["texturl"] ? file_get_contents($json["texturl"]) : null));
 
+    foreach ($json["placeholders"] as $placeholder) {
+        $html = str_replace("{".strtoupper($placeholder["name"])."}", $placeholder["value"], $html);
+        $text = str_replace("{".strtoupper($placeholder["name"])."}", $placeholder["value"], $text);
+    }
+
     $mailer->isSMTP();
     $mailer->Host = $MAIL_HOST;
     $mailer->SMTPAuth = (bool) $MAIL_USER;