For years and years, I've been running my own email server on my home network. Thanks to getting a Nexus 4, I've finally switched everything over to Google, and decommissioned my email server. Now I'm having trouble getting administrative emails (think logwatch, RAID health checks, and the like) delivered out to my Google account.

I have a single internal relay which bounces email out to the world through Comcast's SMTP relay. So I can send email to my account on Gmail, but it will all look like it came from a single address. What I can't seem to sort out is a way to tell which machine the email came from. I have a "proper" network at my house, with an internal domain name and name server. I'd like to be able to see email come into my Gmail account with a {user}@{machine}.{domain} address, but Comcast won't deliver mail with my a local machine + domain name. Failing this, I tried using {machine}@{domain}, but this was also failing with my internal domain name.

I can fake mail to look like it's coming from my actual, real domain, but I was still losing the machine information.

I suppose more options open up if I use my real Gmail credentials, send straight to Google's SMTP server(s), and bypass Comcast's? I'd probably have the same trouble with my internal domain with their servers, though.

I was fooling with nullmailer, ssmtp, and postfix. I know I could work out the simplest working solution through trial and error, but I also know that will take many more hours of screwing around. Someone's bound to have sorted out something clever for this, but I can't seem to find anything through Google. This is probably a dupe, but I couldn't find anything even close on SuperUser or ServerFault.

Maybe it's time to take out another real domain? I'm pretty partial to this one. Or maybe I could use my DyDNS name internally? Comcast and/or Google may respect that one.