>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.

Here, I can not connect to 139.103.2.3.  I'm guessing umoncton.ca is one of 
these extremely poorly designed domains that intentionally has a wasteful 
MX record that goes nowhere (read: they have clueless admins).

>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."

The problem here is with Symantec.  They are translating umoncton.ca's "You 
aren't allowed to connect here" (which IMail properly handles as a "try the 
next MX record" response) into "The server is shutting down -- please try 
again before contacting the next MX record).

In this case, Symantec is definitely in the wrong.  See 
http://www.mail-archive.com/[email protected]/msg48276.html for 
more details on this Symantec problem (from February -- 6 months later, 
they still haven't fixed their problem).

421 specifically indicates a *temporary* error per the RFCs -- Symantec is 
returning this when there is an error that is permanent.

                                                    -Scott
---
Declude: Anti-virus, Anti-spam and Anti-hijacking solutions for 
IMail.  http://www.declude.com

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