SMTP relay through GMail overrides "from:" address with "[me]@gmail.com"
Solution 1:
I think they've always done this, even when you've configured your gmail to send from other domains. As far as I know, the only way around this is to switch to using Google Apps, which is free if you just use the standard edition. The problem with this is that it means you have to change your MX records so that google handles all of your incoming mail, and it is only free for up to 50 users.
Solution 2:
Did you add your non gmail address on https://mail.google.com/mail/?shva=1#settings/accounts ? (in the Send mail as part)
Solution 3:
They do that for security reasons. Your ISP probably uses gmail as they email system, I know mine does. If you want to run a mail server without this issue try smtp2go. It is a small annual cost but it works like a charm! My server has about 5 users and I pay I think about $24.95 a year.
All you need to do is log in to sptp2go and specify what email address are allowed to use the smtp2go smtp server (your email users on your mail server) by email address and then set up your MTA.
SMTP2GO even can runn on different ports. Especially useful if you ISP blocks certain ports.
Solution 4:
I've experienced this as well, and I don't think there's a way around it aside from switching to GAFYD