From what you have posted this looks more like an SMTP problem than ISA. However, I say that with my fingers crossed.
The SMTP filter causes problems with the AUTH command, and thatĂs how you send authentication strings to servers, so disable that first and try again. Other than that caveat, here is what I have for you...
I looked at the error codes you posted and came up with the following:
"Numerical Code: 5.7.1
General access denied, sender access denied ű the sender of the message does not have the privileges necessary to complete delivery.
You are trying to relay your mail via another SMTP server and it does not permit you to relay.
The recipient might have mailbox delivery restrictions enabled. For example, a recipientĂs mailbox delivery restriction was sent to receive from a Distribution List only and non-memberĂs email will be rejected with this error.
Troubleshooting: Check system privileges and attributes for the contact and retry the message. Also make sure you are running Exchange 2000 Service Pack 1 or later for other potential known issues. "
And from Q256321
"5.5.1 Invalid command"
This looks like MessageLabs is not accepting your RCPT to: field as an acceptable address to relay to. While I doubt they are using Ex2k for their server, the codes are fairly standard.
In Q274638 it states that servers that try to send mail without authentication will get a 5.7.3 error as well, so you may need ask MessageLabs what authorization method they have set for you to relay through them.
Also, this error can be linked to a server whose external address changes. You don't mention how your external interface is configured, but if it uses DHCP the IP declared relay at MessageLabs would fail when your IP changes.
Hope this helps,
[This message has been edited by Dominicon (edited 24 September 2001).]