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Author Topic: SMTP client failed to send email  (Read 6509 times)

kellergj64

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SMTP client failed to send email
« on: November 29, 2009, 01:48:07 PM »
I have my DIR-855 router, Firmware Version : 1.12,  2008/10/17, behind another firewall. Why is a SMTP connection attempted with TCP stateless packets? I cannot open my firewall to allow E-mail logs from my DIR-855 without compromising security by disabling stateful packet inspection on the rest of my network.
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MrC

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Re: SMTP client failed to send email
« Reply #1 on: December 01, 2009, 06:06:37 PM »
This doesn't make sense.  SMTP connections are TCP-based, which by definition have state.  Unfortunately, the  DIR-855 only sends email to servers on the the WAN port; perhaps you have been looking for connections on the LAN port?
« Last Edit: December 01, 2009, 06:09:54 PM by MrC »
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kellergj64

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Re: SMTP client failed to send email
« Reply #2 on: December 05, 2009, 04:12:56 AM »
I have the DIR-855 WAN port connected to my hardware firewall which then goes to another modem/router. It does not have any trouble finding my SMTP server using DNS through the WAN port. My firewall is complaining that the sequence number is either incorrect or missing from the TCP header comming from my DIR-855.
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MrC

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Re: SMTP client failed to send email
« Reply #3 on: December 06, 2009, 08:05:43 PM »
This kind of trouble would be curious of it only occurred with SMTP, and not other TCP-based protocols.  Have you verified both ends of the hardware and the cable itself?  Any TCP errors?

The sequence number is the TCP sequence number that is required to assemble the packets into a meanful sequence.  Since the SMTP message payload (data stream) is simply encapsulated within the TCP segment, this problem shouldn't appear with just SMTP.
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kellergj64

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Re: SMTP client failed to send email
« Reply #4 on: December 09, 2009, 02:38:03 AM »
I have experienced no issues other than the SSL login/SMTP TCP sequence number issue that I have mentioned. Other branded, non D-Link, equipment on the same subnet send E-mail without any issue to the same account. The DIR-855 has worked flawlessly for me except for sending E-mail. I just purchased a DNS-343 and as of 1.03 firmware, SSL and port cannot be specified for SMTP. Maybe I just have to set up an unsecure E-mail account for D-Link products.
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