Send Merge Field Of Custom Object Through Email Template Using Apex

If you want to send merge fields of a custom object from Email template via apex you must have to follow the following steps in below.

1. Create a Custom Object and Relationships fields

You can Create fields according to your requirement but at least one field must be Lookup or Master-detail relationship because Salesforce doesn’t allow to replace the merge field from the template so we need to create this relationship field which is described in below because Only Contact, Lead, or Person objects are allowed for targetObjectId.

eg:

CustomObject

2. Create Records of Custom Object

You have to create records of that object. eg: sample record

3. Create Email Template with Merge Fields of Custom Object

Go to Setup -> Email-> Classic Email Template
create a new Email template and write the merge field of the custom object according to your need. eg: Sample

4. Create Apex Class to send Email

Here I am creating an apex class CustomObjectEmailExample which will be called from Visualforce page. You can utilize it according to your business scenario.

CustomObjectEmailExample Class

 /**
  * Webkul Software.
  *
  * @category  Webkul
  * @author    Webkul
  * @copyright Copyright (c) 2010-2016 Webkul Software Private Limited (https://webkul.com)
  * @license   https://store.webkul.com/license.html
  */
public class CustomObjectEmailExample {
	public PageReference sendingMail() {		
        Messaging.SingleEmailMessage mail =  new 
        Messaging.SingleEmailMessage();// create instance of 
         SingleEmailMessage class
	String[] sendingToBccAdd = new String[] 
        {'[email protected]'}; // Add email addresses to blind 
        carbon copy (BCC) addresses. The maximum allowed is 25.
       mail.setBccAddresses(sendingToBccAdd);
       String[] sendingTocAdd = new String[]{'[email protected]'};  
       // add addresses to carbon copy(CC). The maximum allowed is 25.
	mail.setCcAddresses(sendingTocAdd);
        mail.setReplyTo(userinfo.getUserEmail());
        mail.setTargetObjectId('xxxxxxxxxxx');// This is the ID of rel 
        mail.setSaveAsActivity(false);
        mail.setWhatId('XXXXXXXXXXXXXXXXX');// This is the record ID
        mail.setTemplateId(template);// This is template ID
        mail.setSenderDisplayName(userinfo.getname());
        Messaging.sendEmail(mail);
	return null;
	}
}

Visualforce Page : sendEmail Page

 /**
  * Webkul Software.
  *
  * @category  Webkul
  * @author    Webkul
  * @copyright Copyright (c) 2010-2016 Webkul Software Private Limited (https://webkul.com)
  * @license   https://store.webkul.com/license.html
  */
<apex:page controller="CustomObjectEmailExample">
  <apex:form >
    <apex:commandButton value="Send Email" action="{!sendingMail}"/>
  </apex:form>
</apex:page>

5. Output of Example

Conclusion

If you want to send mail through existing object which has a large number of records then you can create relationship (lookup/master) and associate with Contact or Lead and you can use flow or batch apex by matching email field of custom object with contact or lead to populate this field because Email of Contact or Lead will be treated as a recipient.

Note: We can create the maximum number of lookup fields is 25 and master-detail field is 2 on a custom object

Support

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