A simple Perl based SMTP proxy that duplicates incoming SMTP messages to two mail servers. This proxy was developed to allow testing of a new server side by side with the current production server using the same message stream.
Note: Rejections from the destination mail servers (address not known, spam) are essentially ignored and not passed back to the sender.
Warning: This proxy accepts all incoming mail. In some circumstances it can cause your mail system to operate as an open relay.
Requires Net:SMTP:Server module
Usage:
SMTPDuplicate.pl server1 server2 listen_port
server1 - first mail server
server2 - second mail server
listen_port - port to listen for incoming connections