If you are prepared to go to the trouble of setting up ALPINE as a mail client, to talk to your existing dovecot IMAP server and postfix SMTP server, you can perform mail redelivery by selecting the email then using the B
command ("Bounce"; I don't know why they call it that).
You will be asked for the address to which you wish to bounce the message; enter your desired recipient's address, press return, and confirm the operation with Y
.
The message will appear in his INBOX with addittional headers similar to these:
Resent-Date: Mon, 11 Aug 2014 08:22:13 +0100 (BST)
Resent-From: Your Name <[email protected]>
Resent-To: [email protected]
Resent-Subject: Re: Original Subject Line Here
There will also be additional Received: from
headers arising from this new SMTP transaction, but all the original header information, including routing, date, subject and so on, should be preserved.
Please note that questions about the gory details of setting up ALPINE, getting it to authenticate against your existing mail server for reading and sending, and so on, are probably off-topic for Server Fault.
It is likely that some other mail clients can do a similar operation, but I can't say how they can be told to do it, nor whether gmail is one of them.