Required Fields For Secure Email

Label	API Name
From Address	cmsecureemail__FromAddress__c
Recipients	cmsecureemail__Recipients__c	Comma separated email addresses in case of multiple recipients.
HTML Body	cmsecureemail__HtmlBody__c
Parent ID	cmsecureemail__Parent_Record_Id__c	Record ID on which you want the Secure Email to get linked.
Record Type ID	RecordTypeId
Reply to Email address	cmsecureemail__Reply_to__c	Should be Org wide email address
Subject	cmsecureemail__Subject__c

Sample Apex Code Snippet to create a Secure Email record


cmsecureemail__Secure_EmailMessage__c oRecord = new cmsecureemail__Secure_EmailMessage__c();
oRecord.cmsecureemail__FromAddress__c = 'from@email.com';
oRecord.cmsecureemail__Recipients__c = 'to@email.com';
oRecord.cmsecureemail__HtmlBody__c = 'Hello Cloud Maven';
oRecord.RecordTypeId = Schema.SObjectType.Secure_EmailMessage__c.getRecordTypeInfosByDeveloperName().get('Outbound').getRecordTypeId();
oRecord.cm_datatransfer__Parent_Record_Id__c = 'Record ID of the Parent Record';
oRecord.cmsecureemail__Reply_to__c = 'orgwide@email.com';
oRecord.cmsecureemail__Subject__c = 'Test Subject';
insert oRecord;