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Mails not going through ISA - 10.Jul.2008 9:45:44 AM

faetont

Posts: 5
Joined: 16.Jan.2008
Status: offline

Hello to all!

We had one big problem with Exchange and ISA recently. Whe have ISA Server 2004 (with SP2) and Exchange Server 2003 (with SP2) behind it. We are using Exchange server for sending and receiving both internal and external mails. Exchange server send mails to the other mail servers on the internet through ISA, and receives mails from internet through SMTP relay on the ISA computer (IIS SMTP service).
On Friday, sending and receiving mails through ISA had suddenly stopped working. And, what is worse, exchange hasn't replied with any undeliverable notice, so we have discovered that mail is not working only on Monday morning. On ISA server there are no errors, just one note in the firewall log with Status field set to "A non-SYN packet was dropped because it was sent by a source that does not have an established connection with the ISA Server computer". Afther this note SMTP protocol going from exchange was blocked on the ISA. Also, about the sime time ISA stopped relaying mail to exchange, but also without any notice. Restart of the ISA computer solved this problem.

Had anynoe had some kind of similar situation, or could help us with answering the question what went wrong? This would be of great help to us.
Just to say that all clients on our network, including Exchange, are SecureNAT clients of ISA.

Thanks you!

Vinko