Intermittent Email Delivery Issues with Proxmox Gateway and Exchange 2016

[alexvlad]

I am encountering an issue with the delivery of certain emails through our mail infrastructure, which involves a Proxmox Mail Gateway as an intermediary before an Exchange 2016 server. While most emails successfully pass through Proxmox and are delivered to recipients on Exchange, there are some emails that fail to reach their final destinations.

From the Proxmox Mail Gateway logs, it's evident that it processes and forwards emails to the Exchange 2016 server successfully. However, the Exchange 2016 server logs show the following message for the emails that fail to get delivered: "{[{LED=250 2.6.0 <email identifier> Queued mail for delivery};{MSG=};{FQDN=};{IP=Proxmox address};{LRT=}]}". This indicates that the email was queued for delivery but then marked as failed.

Interestingly, when the Proxmox Mail Gateway is bypassed and the Exchange 2016 is directly exposed to the internet on port 25, the problematic emails are delivered without any issues. It's worth noting that the sender's domain is whitelisted.

I would greatly appreciate any suggestions or recommendations to help resolve this issue. Are there any specific settings on Proxmox Mail Gateway or Exchange 2016 that I should look into?

Thank you for your time and assistance.

 

[Stoiko Ivanov]

I would greatly appreciate any suggestions or recommendations to help resolve this issue. Are there any specific settings on Proxmox Mail Gateway or Exchange 2016 that I should look into?

I would check the Logs on the Exchange server - as the log-line (from what I can read - since the "anonymization" quite ruins the context) indicates that Exchange accepted the mail and is responsible for delivering it further

There are quite a few threads in this forum, with users linking to the appropriate documentation from Microsoft about how to configure Exchange for accepting mails from a proxy like PMG

I hope this helps!

 

[alexvlad]

I would check the Logs on the Exchange server - as the log-line (from what I can read - since the "anonymization" quite ruins the context) indicates that Exchange accepted the mail and is responsible for delivering it further

There are quite a few threads in this forum, with users linking to the appropriate documentation from Microsoft about how to configure Exchange for accepting mails from a proxy like PMG

I hope this helps!

the problem is that without Proxmox it works and accepts

 

[Stoiko Ivanov]

the problem is that without Proxmox it works and accepts

that can very well be - and it can still be an issue with the Exchange configuration - see e.g.:

https://forum.proxmox.com/threads/n...ejected-undelivered-emails.103659/post-446275

 

[alexvlad]

that can very well be - and it can still be an issue with the Exchange configuration - see e.g.:

https://forum.proxmox.com/threads/n...ejected-undelivered-emails.103659/post-446275

I disabled all filtering on exchange 2016. did not work

 

[Stoiko Ivanov]

As said - the logs you shared indicates that Exchange accepted the mail - you need to check the logs of Exchange to find out what happened with that mail...

 

[alexvlad]

As said - the logs you shared indicates that Exchange accepted the mail - you need to check the logs of Exchange to find out what happened with that mail...

there is no information in the logs. this is the maximum I found "EventId : FAILRecipientStatus : {[{LED=250 2.6.0 <1240712556.1883.1706103820160.JavaMail.?@api-57-mj6h5> Queued mail for delivery};{MSG=};{FQDN=};{IP=192.168.0.112};{LRT=}]}"