Problem with SMTP mailing

[Milobil]

Hi,

I'm trying to send emails through SMTP on my forum but it doesn't work.

When I make an email diagnostic, here's what i get :

The following errors were outputted by PHP when attempting to send mail:

Warning: 554 Unexpected response from SMTP server when ending transmission in [path]/includes/class_mail.php on line 713

Line 713 corresponds to this : trigger_error($msg, E_USER_WARNING);

What's really strange is that when i use the same SMTP details on my other forums it works really fine and I receive vbulletin's mails. I have also tried with other SMTP logins (that work fine) however in my current forum it doesn't work at all and give the same error 554 above.

Thanks for helping me

[Dave]

Check if the server you're attempting to send the emails from is not blacklisted on spamlists.
http://mxtoolbox.com/blacklists.aspx

[Milobil]

Any way of bypassing this blacklist to send emails ?

[Dave]

No, that's the point of a blacklist.