We've been experiencing what appears to be an mx rollover issue with Imail
since installing a Symantec Enterprise Firewall 6.52 (aka Raptor).  For
those of you unaware of SEF, it's an application proxy firewall, so all smtp
traffic runs through an smtp proxy.

Our daily Imail logs contain a number of "421, unable to contact destination
SMTP daemon" errors.  For some the error only occurs once or twice and then
the email is delivered - this seems normal.  Some, however, have the error
occur every retry.

The umoncton.ca domain is a perfect example.  Here are umoncton.ca's mx
entries:

umoncton.ca     MX preference = 20, mail exchanger = cujam.ci.umoncton.ca
umoncton.ca     MX preference = 10, mail exchanger = altair.ci.umoncton.ca

cujam.ci.umoncton.ca    internet address = 139.103.2.10
altair.ci.umoncton.ca   internet address = 139.103.2.3

Our logs show attempts to connect to 139.103.2.3 only.  Interestingly, I
cannot telnet to 139.103.2.3, but I can to 139.103.2.10.

Symantec's knowledgebase has an entry on mx rollover issues, and blames the
smtp server.  It states: "Some mail servers will not roll over to the second
MX record because they do not properly interpret the 421 SMTP error message
returned by the firewall. The mail server believes it has already made a
successful connection with the remote mail server when it has only
communicated with the Raptor Firewall's SMTP proxy. The SMTP server will not
even try the second MX record."

I'm looking for any ideas you may have.

Thanks

Joshua Pich�
Systems Administrator
CAUT

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