550 5.7.1 relay emial error

[Corné]

Hi,
I have a problem with email sending of one or two of my users. They use
Microsoft Outlook 2003 on their desktop PC's, theres only one account setup
on Outlook. The problem is that one day he/she can send to a specific email
adres and tomorrow he/she will recieve the following error from the exact
same adres.

Error: Your message did not reach some or all of the intended recipients.
Subject:
Sent: 2007/03/20 10:04 AM
The following recipient(s) could not be reached:
Raymond van Jaarsveld ([email protected]) on 2007/03/20 10:04 AM
550 5.7.1 <[email protected]>... we do not relay
<[email protected]>

We do not use Microsoft Exchange Server for our email... but use Merak.

Can you please help as I dont know anymore! I have tried a number of
solutions.

Thanks

 

[K. Orland]

Error 550 is a permanent fatal error. It means the email will never go
through.
Error 5.7.1 is a permissions problem:

Permissions problem. For some reason the sender is not allowed to email
this account. Perhaps an anonymous user is trying to send mail to a
distribution list.
Check SMTP Virtual Server Access Tab. Try checking this box: Allow
computers which successfully authenticate to relay
User may have a manually created email address that does not match a System
Policy.