Hi,

This is a followup to a serverfault post I made a while ago:

http://serverfault.com/questions/21633/how-do-i-target-a-different-mail-server-depending-on-domain-with-exim

(More context here too: http://forum.slicehost.com/comments.php?DiscussionID=3806 )

I have a slice/VPS at Slicehost. I basically decided to scrap exim (i.e., purge it), and start anew with my email infrastructure. In case you didn't read any of the above threads, basically my goal was to have a send only mail infrastructure that relays all outgoing email to Google Apps. I also wanted to where email from domain1 (a Wordpress installation) would show it coming from domain1.com and email from domain2 (a normal website) would show it coming from domain2.com.

So I decided to give PostFix a try. I literally followed the surprisingly simple instructions here:

http://sudhanshuraheja.com/2009/02/slicehost-setup-outgoing-mail-google-apps-postfix/

And voila, all seems to be working as I expected. My email tests show email coming from the proper locations (either domain1 or domain2 depending on where the emails were sent from).

But this all seemed too simple to me. So simple, in fact, that I feel that something is amiss.

When I installed PostFix according to the instructions in the post above and it worked, I was surprised that I didn't have to specify an SMTP server, a port number, any authentication credentials, etc. My slice is set up such that I have MX records for Google Apps (e.g., ASPMX.L.GOOGLE.COM.) in my DNS settings, but I am not sure if that is why it is working.

My email infrastructure knowledge is admittedly limited, but with this am I suspect to:

1. Spammers using my email infrastructure?
2. My emails going to people as spam?
3. Something else sinister?

I have actually stopped running PostFix until I understand this better.

Thanks!