Web Hosting Talk : Web Hosting Main Forums : Hosting Security and Technology : Weird bouncing email problem with some servers

[-OY-]

Hello everybody,

I have some weird problems with email bouncing for a catch-all account.

I've set up a catch-all email account that pipes into a PHP file - lets' call this *@test.hello.com which pipes to |/home/test/test.php

Whilst majority of the email sent to anything @test.hello.com works and goes through the PHP script, some emails sent by some servers bounces with this problem:

Hi. This is the qmail-send program at xxxxxx.xx***********.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<hello@test.hello.com>:
123.123.123.123 does not like recipient.
Remote host said: 550 No Such User Here"
Giving up on 123.123.123.123.

I'm not sure why it gives a 550 No Such User Here error here when it's suppose to be a catch-all account?

Thanks in advance,
Otto

[Ankheg]

Are there any similarities with the e-mail addresses involved? Are they all sub-4 characters? Do they have periods in them? Start with a number?

Depending on the mailserver on your end, the error message may be misleading, and it might actually be a problem with the sender's address/host (SPF failure, bad EHLO, DNSBL failure...) and not the recipient. (This is fairly prevalent with some Exim ACLs, and at least one Qmail patch.)

[-OY-]

Well, the same email address ie. test-123-abc@test.abc.com that bounces on one server and not several others. The problem here is I can't really debug what's wrong with the sender's host, because I have no control over it - it's user's shared hosting account. The only problem or commonality between them is that I'm dealing with customers using H*stgator accounts.

[Ankheg]

If that's the case, I'd strongly suspect your MTA is actually rejecting them for some arcane but identifiable reason - bad/missing/generic PTR, SPF failures, DNSBL hit, et cetera - and giving an incorrect (550) SMTP status in return. Without seeing some actual examples it's impossible to be certain, but that's my guess.

[-OY-]

Thanks for the help. I'm guessing it's one of those as well, I'll have to ask for some bouncing email examples.