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Strange behaviour after R80.20 upgrade

Ever since upgrading our Checkpoints to R80.20 (from R80.10) we are having some issues with receiving mail from certain sources (which so far seems to be Microsoft).

For instance if I try the following test:

I get:

Attempting to resolve the host name X in DNS.

       -The host name resolved successfully.

Testing TCP port 25 on host X to ensure it's listening and open. 

       -The port was opened successfully. 

 Analyzing SMTP Capabilities for server X:25

      -SMTP Capabilities were analyzed successfuly.

                250-SIZE 26214400
                250 DSN

Attempting to send a test email message to X@X using MX X.

                -Delivery of the test email message failed

The server returned status code -1 - Failure sending mail.
Exception details:
Message: Failure sending mail.
Type: System.Net.Mail.SmtpException
Stack trace:
at System.Net.Mail.SmtpClient.Send(MailMessage message)
at Microsoft.Exchange.Tools.ExRca.Tests.SmtpMessageTest.PerformTestReally()
Exception details:
Message: Unable to connect to the remote server
Type: System.Net.WebException
Stack trace:
at System.Net.ServicePoint.GetConnection(PooledStream PooledStream, Object owner, Boolean async, IPAddress& address, Socket& abortSocket, Socket& abortSocket6)
at System.Net.PooledStream.Activate(Object owningObject, Boolean async, GeneralAsyncDelegate asyncCallback)
at System.Net.ConnectionPool.GetConnection(Object owningObject, GeneralAsyncDelegate asyncCallback, Int32 creationTimeout)
at System.Net.Mail.SmtpConnection.GetConnection(ServicePoint servicePoint)
at System.Net.Mail.SmtpClient.GetConnection()
at System.Net.Mail.SmtpClient.Send(MailMessage message)
Exception details:
Message: A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond x.x.x.x:25
Type: System.Net.Sockets.SocketException
Stack trace:
at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot, SocketAddress socketAddress)
at System.Net.ServicePoint.ConnectSocketInternal(Boolean connectFailure, Socket s4, Socket s6, Socket& socket, IPAddress& address, ConnectSocketState state, IAsyncResult asyncResult, Exception& exception)

Elapsed Time: 21010 ms


Microsoft seem to be the only connections coming in with the ECN,CWR flags set.


If we trace the external Interface we can see SYN,ECN,CWR packets come in from Microsoft:

10:28:46.056526 IP > x.x.x.x.smtp: SWE 3702938783:3702938783(0) win 8192

If we trace the internal interface we see a RST packet going to the Load Balancer:

10:02:52.605181 IP > x.x.x.x.smtp: R 3928789066:3928789066(0) ack 0 win 0


We do not have MTA setup

Any ideas?


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2 Replies

I would involve TAC here...

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I have but awaiting a response.

Figured I would post on here in case anyone else has experienced similar issues or has any suggestions on where to look.

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