Multihomed network, mail not going out properly (Full Version)

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EricTheRed -> Multihomed network, mail not going out properly (6.Dec.2006 10:31:51 AM)

Hello all, first post.  Here is the situation, my exchange 2K server has a default gateway of x.x.x.y, and that is where all of its communications should go thru.  I have received 2 complaints from an internal user who is sending to the same recipient where the message is bounced back with the following error..

There was a SMTP communication problem with the recipient's email server.  Please contact your system administrator.
           <servername.domainname.com #5.5.0 smtp;521-EHLO/HELO from sender xx.yyy.zz.ab does not map to servername.domainname.com in DNS>

The ip xx.yyy.zz.ab is my second route to the internet and has a default gateway internally of x.x.x.z.   I do not understand how any mail would ever go out that path,  I tracerouted from the exchange server and it took the path that I had intended it to go.  Even if I take down the gateway device at x.x.x.y  the mail just queues up and doesn’t leave.  Any ideas on how to troubleshoot this issue would be appreciated.

Thanks all, Eric



jchong -> RE: Multihomed network, mail not going out properly (7.Dec.2006 10:16:52 AM)

See if this clear things up.

Myth 4: Virtual Server IP Address Will Be Used For Outgoing Connections
The last source of misunderstanding is the socket which will be used to open an SMTP connection. This may seem confusing and somewhat contradictory of my first point, but SMTP simply tells the Windows network stack to provide SMTP with a socket. It does not provide a source IP address to use, and as such, you will notice that the source IP address assigned by Windows will be based on the Windows routing table, not taking into consideration the IP of the SMTP VSI that is delivering the message.  A common observation of this is that on a cluster server we are using the physical machine IP as our source IP, not any of the virtual IP addresses.

http://msexchangeteam.com/archive/2005/02/25/380481.aspx



EricTheRed -> RE: Multihomed network, mail not going out properly (7.Dec.2006 11:23:58 AM)

JChong, thanks for the reference.  I did a route print on my server and indeed did find a reference to the x.x.x.z gateway with a metrix of 3 the x.x.x.y gateway has a metrix of 1.  I removed that gateway (lets see if any of my remote office VPN users loose the connection to the server, as that is their gateway) and we will see if the issue is resolved.  I is such a intermittent issue (reported only two times this year) that it may be awhile before I can consider this task closed.

Thanks again.
-Eric



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