I have created an apex class and email service that handles inbound emails and associates them to a record based on a match in the email subject. The idea is to mimic email to case functionality for my custom object and it is working fine except for one thing. The Apex class checks the subject line of the incoming email for a matching record in salesforce. If the receiver of the initial email deletes or alters the unique field in the subject before replying, then the email is not matched.
I would like to be able to either insert the field into the email Header/Footer or make the merge field Invisible so that it is not going to be deleted.
Is it possible to hide a merge field in an email template sent from salesforce?