Disabling smtp authentication for local mail on same domain

Question

I am very new to smtp and am looking for something to deal with the current situation:

I have several servers running really old software (music automation) and they all need to report in daily via email. Unfortunately, this software is only able to deal with unauthenticated smtp, so they can't use an smtp server that requires a password. Also, none of them are on static IPs so I can't whitelist them either.

This is what I would like to make happen...

Let say one of the servers will be emailing reports from [e-mail]. The reports will go to [e-mail] which will be an alias forwarding to my real email address.

The question is: Is there a way to make this happen? I need an smtp server that will allow outgoing emails without authentication but I don't want an open relay. Just something that will allow emails to accounts and aliases within the same domain, foo.com.

Does smtp have a setting for this? Does any software provide this functionality? I've been thinking about writing a program/script to solve this problem but I don't even know where to start. Any ideas would be highly appreciated.

By the way, this will be running on a VPS from wiredtree.com.

Thank you!

Answer 1

You could set up a small SMTP daemon (one per server) and tell the music daemon that its SMTP server is "localhost".

The daemon would bind and only listen on 127.0.0.1, and then would send outbound emails to its smarthost using regular authentication:

MusicDaemon --> unauthenticated --> local SMTP daemon --> authenticated --> real SMTP

You can write such a daemon by yourself - some Python required - or you can check out one of several possibilities.

Update

If you can do anything on the SMTP server, why not open it and/or tell it to handle yourdomain.com domain? That way, the server would not require authentication for the mails directed to that domain, while continuing being a closed relay (i.e. requiring authentication) for the emails directed elsewhere.

You can add some kind of filtering to reject all unauthenticated inbound emails except those pertaining to the reports. It shouldn't be necessary, however.