Resolved Forwarded email not arriving

[themew]

Scenario:

Domain1.com hosted on VPS server secured with Plesk and inbound/outbound POP email works perfectly

Domain2.com is a domain only used for receiving email with no hosting so domain registrar forwards all email from Domain2.com to Domain1.com

This has worked perfectly until Plesk update 41/42 (both updates automatically updated at the same time on Mar 02).

Now any email sent to Domain2.com never arrives at Domain1.com, however changing the forwarding at the domain registrar from Domain1.com to forward to Googleemailaddress.com arrives in Gmail.

It is currently impossible to receive email from Domain2.com to Plesk hosted Domain1.com

No email settings or addresses were changed on the Plesk server, all Domain1.com email as well as alias email, SPF, DKIM etc is working great -- the only issue is forwarded email from Domain2.com through the domain registrar to Domain1.com, which only completes using Gmail.

There are no emails on the Plesk server being held, and the original email sent to Domain2.com is not refused or returned to the original email sender.

Based on the last email that did complete, the date coincides with the last Plesk update.

Never seen this before... Any ideas?

 

[themew]

Update: Just received the bounced email header. Looks like the forwarded domain email was being sent to port 25 on the Plesk server which is closed so the email never arrived.

Not sure if the last 2 Plesk updates closed port 25, or the VPS host closed it or the registrar changed port to 25. I don't recall closing it.

The mystery continues...

 

[Bitpalast]

Port 25 is the standard SMTP port. It should never be closed and is unlikely to be closed in a firewall. A block is definitely not introduced by a Plesk update. You can check Plesk firewall or iptables on the server to find out whether it is blocked there.

I cannot imagine how it is possible to get a bounced mail when port 25 is blocked, because in that case the mail would normally not reach the SMTP server in the first place and an answer could not be received by it either, because the port does not work. Could you please provide the header for further analysis?

 

[themew]

Thanks for the reply Peter. Port scan shows port 25 is open and working. Something seems to have changed with the domain registrar that is forwarding domain email without hosting to our Plesk server.

I'm going to go ahead and mark it as solved since it doesn't seem like a Plesk issue.