Update: As you don't have to construct a MIME message, but only have to resend the mail to another address, that doesn't really apply to this case, does it? OK, second choice: Net::SMTP. As somebody else already wrote: you don't have to alter anything in the message, not even the To: header. SMTP doesn't parse the message, either. The recipients are set using the to() method, the message itself, headers and body, can be sent using data().

You do need a live connection to an SMTP server, and it requires you to set some custom values, such as the server, your own domain, and so on. Most servers don't accept mail just from anybody or to anybody, so it could be tricky to get it to work. And it might pose some restrictions on the acceptable email address format.