Random/Sporadic email domains failing Exchange TLS Communication after Microsoft Exchange 2003 to 2010 Upgrade


We recently upgraded one of our clients from Exchange 2003 to Exchange 2010.

Exchange Server Info:
Exchange version: 2010
Exchange Serice pack: SP3
Certificate: GoDaddy
Default Send Connector: TLS optional'
Email routing: Via DNS (smart host not used)

The majority of email sends without issue, but email to sporadic domains just sits in the queue retrying.

Troubleshooting Steps:
I found the out where the issue was occurring when I turned off optional TLS on the send connector. After restarting the Exchange Transport service, the mail queues emptied, but this is only a work around.

In the SMTPSend logs I can see TLS communication running successfully for the majority of domains, but for the trouble domains, I can see a successful initial connection to the remote SMTP host, and the exchange of certificates showing the correct host DNS entries, but then the data payload is empty and the connection retries.

I can also successfully connect to the remote SMTP servers via telnet on port 25, and send a test email to a recipient via EHLO.

Has anyone had TLS issues before after upgrading an Exchange 2003 server to Exchange 2010?

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Jon BrelieSystem ArchitectCommented:
Are your send connectors set to use only TLS connections?

Set them to use both.  Exchange will use TLS when available, but will fall back when it's not.
cpadmAuthor Commented:
The send connector is configured as per the default setting of "TLS Optional".
Simon Butler (Sembee)ConsultantCommented:
When the messages are in the queues, what does the queue viewer actually say?

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cpadmAuthor Commented:
The error on the emails in the queue are:

Delivery is delayed to these recipients or groups: Diagnostic-Code: smtp; 400 4.4.7 (TLS)
Simon Butler (Sembee)ConsultantCommented:
TLS is down to the receiver. Your SSL certificate doesn't come in to it.
That error means the TLS communication wasn't successful, and is usually down to a misconfiguration on the receiving side.

Do check to begin with though that nothing you have is scanning the SMTP traffic. Firewalls for example often do this.

Can you confirm exactly what setting you are changing for this:

"Default Send Connector: TLS optional"


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cpadmAuthor Commented:
We're using Trend Micro DeepSecurity 8.0 that has a number of bugs - After switching the Exchange server to unmanaged, the problem mysteriously vanished... I'm off to study Exchange 2010 antivirus folder/file exclusions....
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