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Not able to receive emails from certain domains. SBS 2003

I am having problems receiving email from certain domains.  We seem to be receiving all email from other external domains just fine.  Every test message that I send to myself is received instantly.  We also have no problems sending email at all.

I noticed one thing, that if I watch the "Current Connections" in the Default SMTP Virtual Server I see a connection from that domain, but no one receives a message.  Eventually the sender will get a bounce back that says the Connection Died.

I read of issues with EDNS and PIX Firewalls so I have tried disabling EDNS on my server, but that did not work.  We are using a Sonicwall TZ 170 for our firewall.

Any suggestions of where to look or things to try would be very appreciated.
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hcasaol
Asked:
hcasaol
1 Solution
 
ATIGCommented:
try to telnet on port 25 to a domain that you are failing to send to: first

1. nslookup <enter>
2. set type=mx
3. domain in question

this will get you the mx of the domain you are trying to reach

telnet domain in question 25

does this connect ? if not there is an issue with connectivity

another problem could be, do you have a ptr record for your sending server that is addressable from the internet?
Verify you are not on any block/black lists
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hcasaolAuthor Commented:
Thanks for the suggestions ATIG, but DNS is fine.  Check for yourself -  My domain is creditfinancialsvc.com.  

The PTR record is mail.creditfinancialsv.com.

I am able to telnet port 25 and send email that way.  

We are not on any black list.
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SembeeCommented:
Do you know what NDR is being generated at the other end?

The issues with the PIX firewall aren't caused by EDNS but by the device intercepting SMTP traffic to see if it is bogus. Some servers don't like what it does to the SMTP handshake. Are there any kind of email filtering options on your firewall?

Simon.
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hcasaolAuthor Commented:
All filtering is disabled on my Sonicwall

The NDR says:
Connected to 204.60.227.65 but connection died. (#4.4.2)

Despite repeated attempts, this message could not be delivered
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SembeeCommented:
That is something interfering with the connection.

What else is on the Exchange server? AV, Antispam? Anything else?

Simon.
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hcasaolAuthor Commented:
Just Symantec AV.

Like I said, I can see a session appear when I watch "Current Connections" in the Default SMTP Virtual Server.  It will usually stay there for up to 300 seconds then disappear.  It will then periodically reappear with no one receiving emails from them.
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ColinRoydsCommented:
try switching on diagnotistic loggin for smtp resend mails from problem domains and check the logs
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hcasaolAuthor Commented:
Here is the log with only connection from that domain.  I put x'x in the addresses to protect the other domain.

http://204.60.227.69/files/4-25_log.xls
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Fordster55Commented:
did you ever get this fixed? I have the same problem
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hcasaolAuthor Commented:
Sorry, I forgot to update the solution.

All I had to do was upgrade the firmware on the Sonicwall TZ 170 to the latest version and everything worked fine.  I think the firewall with the older firmware had problems with MTU size.
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SembeeCommented:
As you found your own solution, you need to get this question closed off by the moderators.
Post in the Support TA (top right corner) with a link to this question asking for the moderators to close the question and refund the points.
Don't accept this as an answer.

(Moderators you might want to delete this comment).

Simon.
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LunchyCommented:
Closed, 500 points refunded.
Lunchy
Friendly Neighbourhood Community Support Admin
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