When I send an email to a user that doesn't exist, Postfix doesn't bounce the message back to the sender. Is there a way to enable this? Thanks!
You should not bounce mails of non-existent users. If you followed the default install, Postfix will reject the mail during the initial conversation at MTA level. Accepting mail and later on send a bounce is called backscatter and is considered bad these days. Google for 'backscatter' and you'll see what I mean.
We get very little spam here, but because we're a small company and could lose a lot of business if someone sent an email to the wrong addy, it would be very good to notify whoever sent the message that we didn't get it.
Normally the sending MTA handles this, if configured correctly. If the sending MTA cannot deliver an email because of a wrongly spelled email address of the intended receiver, the sending MTA should inform the sender, based on the rejection response of the received MTA (your Postfix). Anyway, that's the policy these days on the internet.
Right now the MTA is returning a user does not exist in the local tables error. Should the servers trying to send to us in that case return an error to their user that our user does not exist? Our server will immediately error our client when we send to a local name that does not exist. I'm understanding that their server, sending email to us, would also receive that error immediately upon failing to send to a non existant user?
Yep, that's correct. The sending MTA (server) will notify the actual sender of the email about the fact that it couldn't deliver the message. So the sending user will get an error, but he/she will get if from their own mailserver.
Cool, ends up our local mailserver is somehow suppressing those emails that we should be getting back, so, testing wasn't working, but if someone actually does email to an invalid addy, they're mail server is returning them an error. Perfect! Does anyone know how to block an email from someone not in a TLD? i.e. .ru? They little spam we get is always from [email protected] or [email protected] or something like that. It'd be nice to not get that anymore, and we have no email that would ever come from outside the US, so, we don't have to worry about legit email outside of .com, .net, .org and .biz
That would effectively block also e.g. the European countries. Maybe you should be aware this board and all the goodies are developed in Germany? I've seen discussions on both the Postfix as well as the Exim mailing lists to just 'block everything that is not in my country'. You can do it with RBL's, but I'm not the one that's going to help you with that.
