Send email to PostFix on LAN

Question

Hi I'd like to have an Exchange server on our network forward mail to a mail server on a local Linux box which uses Postfix/Dovecot.

To give some context, there is an Exchange server on premise that we would rather avoid interacting with directly as we don't manage it. One email account receives emails, which we would like to download and process into the system we manage. So we thought it would be a low impact solution to set up a Linux box locally and have the mail forwarded to that. We've got a basic thing set up but we're unsure how one forwards locally on a LAN. Plus I thought it would be fun to tinker with Linux as I'm a developer. If this is a terrible idea by all means say!

I'm a newbie to this so I followed this tutorial

https://www.linux.com/learn/how-build-email-server-ubuntu-linux

Which "works" - in that I used telnet to send an email to ubuntu_user@serverhostname and I have set up Thunderbird to read the mail.

So next question would be what address would the Exchange server need to use to send the mail? And can anyone recommend a good way to test sending mail locally. I'm a little unsure how a mail client like Outlook (using e.g. Office 365) or Exchange - will interpret a local email address. Cheers, Chris.

Answer 1

Exchange doesn't route email based on the specific recipient, but only on the recipient's domain. Therefore the only way you can do this is use another domain. That could be a completely dummy domain (domain.local) or a subdomain (host.example.com - where example.com is your primary domain). Then configure a Send Connector with the remote domain configure as the one you have setup, and set it to use a smart host which is the IP address of the other server. You can then forward email to an email address at that domain using rules, mail forwarding etc.