Thank you, gentleman.

Since I was able to circumvent the issue and as Mark said, it's now more of a 
networking issue (probably w/Verizon and to get them to correct it would take 
hours of phone calls) I'm going to leave the issue as you said, to another time 
(sic: group).


Thank you for your assistance!!!!

Wayne

-----Original Message-----
From: Mark Lawrence <[email protected]> 
Sent: Friday, April 25, 2025 2:31 AM
To: Wayne Spivak <[email protected]>
Cc: [email protected]
Subject: Re: MTA stopped connecting to Postfix server on 587

> tcpdump -n -v host sbanetweb.com and port 587 tcpdump: listening on 
> eth0,

This filter is too narrow to capture icmp traffic, for which the concept of a 
port does not apply, and because the source address could belong to some switch 
or router. Better would be:

     tcpdump -n -v 'icmp || tcp port 587'

As Betarays said, a traffic capture on the destination would also provide more 
light. Host- and port specific filtering is ok and probably necessary there to 
minimize the noise.

> Could a) rebooting the switch and b) rebooting the router at the NAS 
> location worth the effort.

In the windows world that seems to often be a solution... but I think it is 
less effort in the long run to identify the root cause and make specific 
changes in response. But the effort/reward trade-off is an individual (or 
organisational :-) calculation.

>MCQ (as does all the servers mentioned) have a internal IP (192 rnage) 
>through a NAT server to different public IP’s.  They also have VPN 
>static ip’s.

Multiple paths and multiple addresses are of course extra complexity, which I 
don't think we on this list are going to easily understand or fix in a few 
words.

>I changed the relay address from my domain/public address to my VPN ip 
>address and mail was sent.
>
>...
>
>Why it's going two different ways (consistently over multiple attempts 
>is bizarre).
>
>What does that say?

That there is clearly a network issue, and not obviously an OpenSMTPd one. So 
this is probably not the right place to solve it \_(ツ)_/.

--
Mark Lawrence



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