SMTP Authentication

[ultimateav]

I have been looking through some of the other threads and could not find an answer to my ongoing problem.

I am running a 1&1 domain aswell as mail servers. I can receive all incoming emails to our domain name through the POP3 connector running on my Exchange 2003 but cannot send outgoing emails, all mails come back undeliverable saying:

There was a SMTP communication problem with the recipient's email server. Please contact your system administrator.

<

http://www.***********systemsltd.co.uk

#5.5.0 smtp;550 must be authenticated>

I have tried several things, such as looking into the SMTP connector and playing with security settings etc but to no avail. Any help would be much appreciated. Thanks.

 

[ultimateav]

Have since changed port no 25 to 587 but still with no luck. Running direct into my Outlook using POP3 with server authentication works and can email external domains, so I know it will work, but it is linking it into my Exchange server settings that I need to double-check. 1&1 won't give me any help at all....somebody please?

 

[rcoulter]

I am experiencing the same issue, but it seems only in relation to messages sent to earthlink.net