Question

I have a system that sends mail.

I have a system that receives mail.

I need to identify that a received mail correlates with the one the other system sent.
The particular thing here is that either the subject or the body can be modified.

I thought on putting some hash in the header of the sent email, but I don’t know where this could be added

Don’t you have any clue?

Answer 1

I’ve finally found the solution:

Most email’s servers support to put something after the username using ‘+’ as separator. So I can encrypt some id and decrypt it when is replied looking on the from address.

example:

[e-mail]

I hope this can help someone else with the same problem