Strange behavior in PHP mail function, address does not exist

Question

I recently had this problem with a client. The code reads:

ini_set( "sendmail_from", " noreply@ <current-domain>.com" ); // $target_email has been validated as a value username. // $subject is a simple String. // $message is an HTML message. mail( $target_email, $subject, $message ); 

When I tested this on my machine, it worked fine. When I tested it at home, at work, in Windows 2000 (IE6), XP (four different computers and a VirtualBox instance) (IE6 and 7, Opera 9, Firefox 3) and Vista (IE 7), as well as through Konquerer and Firefox on Ubuntu (on two different machines), it worked fine (I don't have a Mac). I tried the website on four different networks and in three different countries. I did everything I could to smash this site, and I did not receive any errors, and the letter quickly appeared from noreply @ <current-domain> .com to the expected address.

When my client checked this at his office, he received an SMTP error stating that the name noreply @ <current-domain> .com does not exist and he did not receive the email. But the same lines work fine when working on my server (the base LAMP is configured to work with PHP 5.3, they have Windows 5.2.6).

What actually happened? My best guess was that this is some kind of fancy problem with a Windows server, I have nothing stupid what else could be. Unfortunately, I could not understand how they set up their local machines to test this theory.

Answer 1

My assumption: the client SMTP server is configured only to relay mail for known (for example: from Active Directory) addresses and rejections (in truth, you can say) of all the other "senders"? Does the customer domain have an existing address?

Try sending mail from a "known" good address [e-mail] , telnet to smtp server ... to try to narrow down the problem.