I have to write an application which processes and forwards mails which are delivered to a default user, but the original sender must be preserved.
But does that also work with users/senders which are not Exchange users?
In other words, this works:
firstname.lastname@example.org ---> email@example.com ---> firstname.lastname@example.org
Jane sends a mail to the default user. My application processes the inbox and composes a new message based on the original message and sends it to John with Jane as the sender.
But how about this:
email@example.com ---> firstname.lastname@example.org ---> email@example.com
In this case an unknown external sender sends the original e-mail. Can the forwarding application still set the sender of the new message to the original unknown sender?
I fear that this is not allowed because that would be a spammer's tactic (although here it is incoming mail, not outgoing)
(Unfortunately I don't have access to an Exchange server in the foreseeable future, so I can't just test this.)