lost connection while receiving the initial server greeting

[YHC]

Dear All,

We have troubles sending email to a specific mail domain with the following error message:

lost connection with mgw.ntu.edu.tw[140.112.8.25] while receiving the initial server greeting

This error happened after we adjusted our Fortigate 30E policy but we have no problems sending emails to other addresses.  Could anyone advise us what kind of policy issues could results in this error?  Or does it simply because of network/connection issues?

Thank you.

[dbu]

Hi @YHC ,
If you have FortiMail try to increase the greeting timeout. The default value is 30 seconds.

 As per RFC 2821 , is  recommended a timeout value of 5 minutes (300 seconds).  Of course you can adjust it lower. 

From CLI:
config system mailserver
   set timeout-greeting <seconds_int>
end

https://docs.fortinet.com/document/fortimail/7.2.2/cli-reference/59838/system-mailserver

[YHC]

Hi,

Thank you.

Unfortunately, I am not using FortiMail.

I found that the SMTP transaction time is pretty long (more than 15 sec.).

Could it be the cause of lost connection?

I am wondering if there anything wrong with our FortiGate 30E setting and results in our  long SMTP transaction time.

Could anyone advise?

Thank you.

[dbu]

Yes it can be connection issue. You might have either delay or drops on the path. 
From Fortigate side i believe there is no timeout option to configure to extend the delay. 

Is it possible to check something similar from the Email server side? 

[Elija]

I too got the same issue

[AEK]

Hello

You can use mxtoolbox.com to check connection time and transaction time of your remote mail gateway (use "Test Email Server" menu).

If the result is good than it is also possible that your FGT's pub IP is simply blocked from mail gateway side. You need to ask mail administrator to check it for you.

[Sheikh]

Hello @YHC 

Have you tried to get the packet capture on FortiGate ?

diagnose sniffer packet any "140.112.8.25 and port XX" 4 0 l <----------change port number accordingly (25, 587,465 etc..).

and reproduce the issue.

regards,

Sheikh

[AEK]

Can you give more details about the configuration the you changed?

Check if your mail reputation is ok.

Also check if you are not simply blocked by your recipient's gateway.

[austinjhones72]

Experiencing email issues can be challenging. The 'lost connection' error may stem from Fortigate 30E policy adjustments or network challenges. Ensure the policy settings align with email server requirements. Verifying network connectivity globalfist and consulting Fortigate support might help resolve the specific domain sending problem.

[janefoster92]

It sounds like the policy adjustments on your Fortigate 30E might have inadvertently affected the way your emails are routed or recognized by specific domains like mgw.ntu.edu.tw. It could be a misconfiguration that's causing these domains to not acknowledge your server's greeting. Checking your SMTP settings and ensuring they align with whatsgb guidelines for secure and reliable email communication might help.