Exchange SMTP connector AUTH rejection

This seems a little odd.

In SBS20003, the SMTP connector has been told to forward email via another server (linux box)
The outbound security is set to basic auth with the correct user name and password set.

The queue status information on this connector states "The remote SMTP service rejected the AUTH negotiation".   I know that normally means the user name or password is not set correctly.  I KNOW the user name and password is set correctly, because I have set additional debug information in the linux mail log that shows me both the connection coming in, along with the username and password being used and confirms that the connection has been accepted.

Yet the Exchange connector still insists that the AUTH negotiation was rejected.

Two questions:
1. Could exchange be incorrectly reporting this error.
2. Is there further debugging information available in the SBS2003  box that may allow me to see more detail of the connection from the Windows end.

There may be a clue in the error message - the NEGOTIATION was rejected rather than password.  Don't know how fine grained the connector reporting would be.


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Just a wild stab in the dark here, but could the issue be on your linux box?
Something like maybe it limits the number of emails it will accept during a given time?
sheepfarmerAuthor Commented:
Did some more testing on this.

- I deleted the SMTP connector
- Recreated SMTP connector
- Changed the SMTP account password on the linux box
- Added Basic auth name and password on SMTP connector
- Send some email from SBS2003 and it worked
- Noted SMTP queue was now empty
- Sent some more email from SBS2003
- This time the queue showed the connector had failed again with AUTH error.
* So, the last email was send through a working connector, but failed.

- Changed SMTP connector to use anonymous SMTP
- Forced queue
- Failed (expected)
- changed SMTP connector to use name/password AUTH
- forced queue - this time the email was sent.

Very confusing!


sheepfarmerAuthor Commented:
I did think about and checked beforehand - there is a limit on the number of concurrent connections in from a specific IP address, but the limit is 6 and in the tests above, there was only one email (therefore connection required).

Is there a way to force Exchange to queue emails to only use one SMTP pipe to rule out that possibility.
Using an SMTP Connector with a smart host configured means that all the email goes down the same connection. Instead of the server looking up each domain, it just sends it to the host listed in the connector.

I was wondering if something was interfering in the SMTP traffic - which would explain the failure message.

sheepfarmerAuthor Commented:
Having done some more research, my current view is that it could indeed be the Linux box causing blocking or throttle restriction.  I am hoping that someone can throw some light on this and I'll report back.

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