Refactor of Postmark CFC from https://github.com/wildbit/postmark-coldfusion/blob/master/postmarkapi.cfc

postmark.cfc

<cfcomponent name="PostMarkAPI" hint="Send email messages using Postmarkapp.com API">
 <cffunction name="sendMail" output="false" access="remote" returntype="struct" returnformat="json" description="Assembles JSON packet and sends it to Postmarkapp">
 <cfargument name="mailTo" required="true" type="string" displayname="Recipient" />
 <cfargument name="mailFrom" required="true" type="string" displayname="Sender" default="xxx@xxx.com" />
 <cfargument name="mailSubject" required="true" type="string" displayname="Subject" default="Testing Postmark" />
 <cfargument name="apiKey" required="true" type="string" displayname="API key" default="xxx-xxx-xxx-xxx" />
 <!--- optional --->
 <cfargument name="mailReply" required="false" type="string" displayname="Reply-To (optional)" />
 <cfargument name="mailCc" required="false" type="string" displayname="CC (optional)" />
 <cfargument name="mailHTML" required="false" type="string" displayname="HTML body (optional)" />
 <cfargument name="mailTxt" required="false" type="string" displayname="Plain text (optional)" />
 <cfscript>
    var response = {};
    var key = '';
    var mail = {};
    var lookup = { 
	'mailTo' = 'To',
	'mailFrom' = 'From',
	'mailSubject' = 'Subject',
	'mailReply' = 'ReplyTo',
	'mailCc' = 'Cc',
	'mailHTML' = 'HTMLBody',
	'mailTxt' = 'TextBody'
    };
			
   // build postmark object			
   for (key in arguments){
     if (key != 'apiKey' && len(arguments[key])){
      mail[lookup[key]] = arguments[key];
     }			
   }
  </cfscript>

  <!--- send to Postmarkapp --->
  <cfhttp method="post" url="https://api.postmarkapp.com/email" result="response">
    <cfhttpparam type="header" name="Accept" value="application/json" />
    <cfhttpparam type="header" name="Content-type" value="application/json" />
    <cfhttpparam type="header" name="X-Postmark-Server-Token" value="#arguments.apiKey#" />
    <cfhttpparam type="body" encoded="no" value="#serializeJSON(mail)#" />
  </cfhttp>

  <!--- status code --->
  <cfreturn {'statusCode' = response.statusCode} />
</cffunction>
</cfcomponent>