So recently I had a user come to me and tell me that certain addresses he's sending mail to give him rejection bounce-backs, but only from his blackberry. I'm thinking it has something to do with an in house mail filter we have installed recently, but why would only the blackberry be affected. these addresses work fine form his computer using outlook. here is the message...

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.
<mail.mycompany.com #5.5.0 smtp;554 Message failed>

Are you using BES?

Yes. we are using BES Express 5.0.1.4

Moved to the BES Admin section.

The "5.5.0 smtp; 554 Message failed" occurs for 2 reasons

1) The IP address does not match the domain name that is used in the return address of the e-mail message.

2) A pointer (PTR) record does not exist or is not valid for the source SMTP server's IP address.

The mail server <mail.mycompany.com> probably thinks the BlackBerry is 'spoofing' the mail server. The mail server <mail.mycompany.com> compares the IP address (which is a BlackBerry Infrastructure IP address)to the domain name of the senders email and rejects the email.

Is the <mail.mycompany.com> the sender's or the recipients? Because that's the server that's having the problem.

The BB infrastructure does not send on behalf of your domain (ie spoofing your mail server) - the mail is still sent through the same mail server it normally does.

Are these internal or external email addresses?