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Exchange 2003 and Verizon FiOS

Posted on 2009-04-02
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Last Modified: 2012-05-06
Very specific issue:

Small Business Server 2003 with Exchange 2003, connected to Verizon FiOS.  Virtual SMTP server is configured to send all outbound messages through Verizon's SMTP server, and the required Verizon username and password are entered and appear to be working.

In addition to hosted mailboxes on the Exchange server, I also have several contacts that redirect e-mail to Verizon.net mailboxes.  These also seem to be operating just fine, except when the sender is a verizon.net address, in which case an NDR is sent back to the sender stating "550 5.7.1 Authentication is required to send mail as <xxxxxxxx@verizon.net>".

This only occurs when the sender is a verizon.net address.  All other internet senders' e-mail is relayed and delivered without issue.

Can anyone provide any insight as to what may be causing this?

Thank you.

Dimarc67
Columbia, MD
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Question by:Dimarc67
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by:Dimarc67
ID: 24063495
Further info--

I've been able to confirm that in the scenario of relaying inbound e-mail sent from a Verizon sender, only e-mail sent under the username and password that is entered in the virtual SMTP configuration is relayed.  But the odd thing is that all e-mail sent from non-Verizon senders is relayed without issue.

Would anyone else besides me speculate that this is some sort of side-effect of Verizon's authentication routines?  Can anyone suggest a solution to this?
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Mestha earned 500 total points
ID: 24065363
Almost certainly it is down to their spoofing controls, and that is pretty clever that they are doing that. It is probably to ensure that users don't spoof as other Verizon users.

As for a resolution, the only one I can think of is to use another server outside of Verizon to bounce the email off. The type of forwarding that Exchange does will make the message look like spoofing.
Another one would be to not use a smart host for email to the Verizon address. Email to Verizon will be entering their network via different hosts, which are setup in a different way to the servers you route outbound email to.

Also it isn't good practise to have the smart host set on the SMTP Virtual server. It should be set on an SMTP connector which will allow you to deliver email correctly.
If you want to try routing email directly via DNS for verizon addresses then you will have to make this change as you will need two SMTP Connectors - one for the smart host and one for the Verizon addresses.

Simon.
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