Errors when sending email via SMG from Exchange

[Tomasz Zielinski]

When Exchange (from Outlook) is sending emails via SMG i have errors in SMG "Abort message (message time out)". Problem was reported to Broadcom Support and after looking at packet capture they found that Exchange send data packet to SMG, SMG sends ACK to Exchange, SMG sends ACK with TCP widow update to Exchange, five minutes after most recent ACK no other packets have been received form Exchang and SMG time out the sesion. 
In Exchange transport service logs I have 

2023-05-18T20:18:41.277Z,SMG,08DB53CAAC00F8FF,21,192.168.45.35:49461,192.168.45.41:25,*,,"HandleError has encountered a suspicious connection reset from a remote, non-mailbox transport server."

From Exchange Queue 

[{LED=450 4.4.318 Connection was closed abruptly (SuspiciousRemoteServerError)} Exchange 2016

Emails sended via OWA are working fine

[alexander smg]

Certificate issues. ?

[Tomasz Zielinski]

After 4 atempts message is sent. To low max connection in Exchange connector?

[alexander smg]

If smg is closing the connection, then it’s smg. I ask again. Tls cert????

[Art_P]

I just said that it wasn't an action from SMG, that's not what "Abort message (message timed out)" means. There's not enough info to indicate a potential cert related issue, I mentioned that the statements about the packets lacked context. However it's not SMG that is closing the connection. 
If it were cert related, it wouldn't likely be directly related to the cert. It wasn't a cert failure, which would have specific responses, it was a timeout due to lack of network packet responses to the Messaging Gateway.

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Support Engineer
* Integrated Cyber Defense Exchange
* Messaging Gateway
* Packet Shaper
Symantec Enterprise Division
Broadcom Software
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[Art_P]

Sounds like something might be between SMG and Exchange that should be looked at. the "Abort message (message timed out)" specifically means that the Messaging Gateway was communicating with the other server but the network connection was lost (not due to direct action from SMG). Your description of the packet capture lacked context, but in general you said that SMG sent an ACK (meaning it acknowledged Exchanges previous packet) and would generally then be waiting for Exchange's next packet, which never arrived - ending in time out.
Your Exchange logs seem to indicate that Exchange thought SMG stopped responding. Thus, most likely culprit is something in between.

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---------------------------------------------
Support Engineer
* Integrated Cyber Defense Exchange
* Messaging Gateway
* Packet Shaper
Symantec Enterprise Division
Broadcom Software
------------------------------

[Tomasz Zielinski]

Description of pacet capture is from Case 33390143. Exchange and VM are in VLAN, same site maybe sometimes different host. But from OWA mails are working. From transport service logs i se that certificate negotiation using tls 1.2 is succeded 

[alexander smg]

The issue is new???
On May 24, 2023, at 10:18 AM, Tomasz Zielinski via Broadcom <[e-mail]> wrote:

Description of pacet capture is from Case 33390143. Exchange and VM are in VLAN, same site maybe sometimes different host. But from OWA mails are... -posted to the "Messaging Gateway" community <https: community.broadcom.com=""> Messaging Gateway <https: community.broadcom.com/symantecenterprise/communities/community-home/digestviewer?communitykey="bba1e9dc-0c56-4fb5-9e3d-ef7f0d79b7ee"> Post New Message <[e-mail]> Re: Errors when sending email via SMG from Exchange <https: community.broadcom.com/symantecenterprise/discussion/errors-when-sending-email-via-smg-from-exchange#bm7a5d48ce-a4de-4d38-afbe-01884e1ab3b1=""> Reply to Group <[e-mail]?subject=re: errors="" when="" sending="" email="" via="" smg="" from="" exchange=""> Reply to Sender <https: community.broadcom.com/symantecenterprise/communities/all-discussions/postreply?messagekey="7a5d48ce-a4de-4d38-afbe-01884e1ab3b1&ListKey=c7074c2b-e593-418f-9d9e-0567f9e41e52&SenderKey=81914f51-0b1c-4fcc-a347-01884c9ab40f"> <https: community.broadcom.com/network/members/profile?userkey="81914f51-0b1c-4fcc-a347-01884c9ab40f"> May 24, 2023 10:19 AM Tomasz Zielinski <https: community.broadcom.com/network/members/profile?userkey="81914f51-0b1c-4fcc-a347-01884c9ab40f">
Description of pacet capture is from Case 33390143. Exchange and VM are in VLAN, same site maybe sometimes different host. But from OWA mails are working. From transport service logs i se that certificate negotiation using tls 1.2 is succeded
Reply to Group Online <https: community.broadcom.com/symantecenterprise/communities/all-discussions/postreply?messagekey="7a5d48ce-a4de-4d38-afbe-01884e1ab3b1&ListKey=c7074c2b-e593-418f-9d9e-0567f9e41e52"> Reply to Group via Email <[e-mail]?subject=re: errors="" when="" sending="" email="" via="" smg="" from="" exchange=""> View Thread <https: community.broadcom.com/symantecenterprise/discussion/errors-when-sending-email-via-smg-from-exchange#bm7a5d48ce-a4de-4d38-afbe-01884e1ab3b1=""> Recommend <https: community.broadcom.com:443/symantecenterprise/discussion/errors-when-sending-email-via-smg-from-exchange?messagekey="7a5d48ce-a4de-4d38-afbe-01884e1ab3b1&cmd=rate&cmdarg=add#bm7a5d48ce-a4de-4d38-afbe-01884e1ab3b1"> Forward <https: community.broadcom.com/symantecenterprise/communities/all-discussions/forwardmessages?messagekey="7a5d48ce-a4de-4d38-afbe-01884e1ab3b1&ListKey=c7074c2b-e593-418f-9d9e-0567f9e41e52"> Flag as Inappropriate <https: community.broadcom.com/symantecenterprise/discussion/errors-when-sending-email-via-smg-from-exchange?markappropriate="7a5d48ce-a4de-4d38-afbe-01884e1ab3b1#bm7a5d48ce-a4de-4d38-afbe-01884e1ab3b1">

[Tomasz Zielinski]

Nope, SMG is only for inbound mail. I want to enable outgoing mails via SMG and this hapens

[alexander smg]

Capture. And pic of errors

[alexander smg]

I also didn’t get your packet capture. I will need that as well please.