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User cannot send to a particular email address

Posted on 2007-12-04
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Last Modified: 2013-11-30
I have an external user (not logged into the domain or LAN) that sends email through my Exchange 2003 mail server. He has a AD user & Exchange account and also a compuserve e-mail account.

When he tries to reply to an email sent to his compuserve account by a customer he gets this NDR:

Content-Type: message/delivery-status

Reporting-MTA: dns;mydomain.office
Received-From-MTA: dns;CAF610
Arrival-Date: Tue, 27 Nov 2007 16:01:27 +0000

Final-Recipient: rfc822;customer@customer.ch
Action: failed
Status: 5.5.0
Diagnostic-Code: smtp;550-Callback setup failed while verifying <user@compuserve.com>
550-(result of an earlier callout reused).
550-The initial connection, or a HELO or MAIL FROM:<> command was
550-rejected. Refusing MAIL FROM:<> does not help fight spam, disregards
550-RFC requirements, and stops you from receiving standard bounce
550-messages. This host does not accept mail from domains whose servers
550-refuse bounces.
550 Sender verify failed

Is it my Exchange server not verifying the user as valid to send because of the compuserve account?

Is it the customer's mail server not verifying the user as valid because it expects mail from compuserve?

Should/How do I set up a SMTP connector and does it leave me vulnerable to spam?

Any help would be grealty appreciated

Thanks

Mat

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Question by:matedwards
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Expert Comment

by:LeeDerbyshire
ID: 20403788
Do you think that this user is sending email that has a CompuServe From address, but is being relayed through your own server?  If anyone is doing SPF checking, then the mail will be refused.
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Author Comment

by:matedwards
ID: 20403836

Yes, his From address is user@compuserve.com

I have set this as an additional e-mail address for user@mydomain.com

Do you think @customer.ch mail server is doing an SPF check against compuserve dns and not allowing the e-mail from mydomain.com?

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Expert Comment

by:LeeDerbyshire
ID: 20403862
That's the only thing I can think of that would account for what you are seeing.
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Author Comment

by:matedwards
ID: 20403890

But there's no mention of a

Remote-MTA: dns; mail-mx-dedotec.ch

in the error.

I would have thought it would be there if they were doing an SPF check?

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Accepted Solution

by:
LeeDerbyshire earned 250 total points
ID: 20403968
I don't know if you would see that or not, I'm afraid.  You could always try a telnet test on port 25 from your location, and see if it gets through when you supply the CompuServe from address.
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Author Comment

by:matedwards
ID: 20403988


good idea.

Will try it now.
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Author Comment

by:matedwards
ID: 20404181


I cannot open a telnet session on port 25 to the customer@customer.ch mail server.

Keep getting a connection lost.

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Expert Comment

by:LeeDerbyshire
ID: 20404205
How far does it get before the connection is lost?  Does it always drop the connection after the same command?
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Author Comment

by:matedwards
ID: 20404283

Yep. When I type  "open customer mail server ip address 25" or use the domain name

Waits for a while and then says "press any key to continue"

And then says "Connection to host lost."
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LVL 31

Expert Comment

by:LeeDerbyshire
ID: 20404344
Seems strange.  Can you tell me the real receiving domain name so that I can try it here?
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Author Comment

by:matedwards
ID: 20404379

dedotec.ch

Should've said it from the beginning really - doh!

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Author Comment

by:matedwards
ID: 20404520

I've just tested it using telnet to an ip address of one of their mail servers.

Another administrator here had blocked port 25 from client ip addresses in my range - apologies.

It appears you're right. They will accept mail from mydomain.com but not if I "ehlo" as compuserve.com

I take it the only way round it is to ensure the user's "From" field is user@mydomain.com?

 
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Expert Comment

by:LeeDerbyshire
ID: 20405863
The correct way would be to get the compuserve.com email relayed through compuserve's own mail servers rather than your own.  Anything else just looks like address spoofing.
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