I have a few devices on my network that are old enough to not understand SSL/TLS, or were designed for an enterprise mail network and don’t provide any authentication. I find it beneficial to run a simple Postfix box configured as a relay for these devices. Postfix accepts email from these items, strips the headers, and re-sends it via something like gmail.
My mail server is 192.168.1.250:25. When I try and enter this in the outgoing mail server settings, it won’t allow me, because it assumes all outgoing servers start with SMTP. While I can set my local DNS to fake a name, it’s somewhat inconvenient because I don’t want to accidentally interfere with an outside resource that may exist in the future.
Is there a way to allow the outgoing SMTP server to be set to an IP address or other, non-SMTP url?