SMTP relay server Recommendations?
Posted on 2011-05-05
I'm looking for suggestions for an STMP relay. Currently, I have servers in a software design lab that need to send mail to my local SMTP server to be delivered. These mails are for password resets, notifications, etc.
Currently I have exchange 2007 running on an old domain which these lab servers can reach on the internal LAN. The exchange 2007 server has rules which state which systems it will relay for and all others that attempt to relay will be denied. Since this was setup, we have been acquired by another company and their mail server is across a WAN link in a different country and the original exchange 2007 server will be retired. The lab servers are on a subnet that cannot reach across the WAN link and directly talk to the mail server (by design) so they can't simply deliver the mail theor for relay.
What I need to do is have the lab servers deliver their mails to an SMTP relay locally which will relay those mails to the companies mail server for delivery to their end destination. The companies mail server will have rules in place to only relay for the hosts configured.
My question is what should I use locally to relay these emails? Preferably one that will keep the same source IP from the server that originated the mail.
I've looked briefly at sendmail and at IIS for doing this. I'm OK with either Windows or Linux software to accomplish this, but I will of course need to permit relaying only for the hosts I specify. I'll simply install the relay software on an existing server in the network. All of the relays will be contained within the companies WAN and the relay server won't be able to touch the internet (no NAT).
The volume of emails to the relay server are expected to be very low.