Double e-mail delivery

[DerDanilo]

Since the cluster setup some e-mails are delived times * PMG members in cluster.
MX Records show same prio or one has higher (therefore lower) prio and servs as backup.

@ IN MX 10 pmg1.domain.de
@ IN MX 10 pmg2.domain.de
@ IN MX 30 pmg3.domain.de

or

@ IN MX 10 pmg1.domain.de
@ IN MX 10 pmg2.domain.de

Looking at the mail header the same email is delivered by each PMG member in the cluster to it's relayed mailserver (so same server).

This happens in several PMG clusters.

@proxmox team
- Is there a mechanism that needs activation in PMG so this doesn't happen?
- I'd think that the PMG cluster is intelligent enough to register that an email already passed through and then stops delivering it.

This is quiet bad, as some users complain about receiving a mail several times, though it's sent only once.

How to solve this?

 

[dietmar]

The sender must not deliver the mail twice. This is an error on the sender side.

 

[DerDanilo]

The sender must not deliver the mail twice. This is an error on the sender side.

Well the sender is currently mainly Google, free and gsuite.
We need to be able to block double mails on our site or do you expect companies to contact Google on this? They won't change a thing there. :-(

 

[dietmar]

AFAIK Google does not send emails twice.

 

[DerDanilo]

AFAIK Google does not send emails twice.

According to the mail header it does.
Don't know why.
This also happens with some other clients (sender is not Google) on a regular basis. Any suggestions?

 

[dietmar]

This also happens with some other clients (sender is not Google) on a regular basis. Any suggestions?

Most email servers filters duplicates by default (or have an option to do so).

 

[DerDanilo]

Thanks for your answer. I am just wondering why this is happening. E-Mailserver is 95% Dovecot/Postfix, so I don't get what causes this problem.
There is no way to manage this via PMG cluster? Isn't it possible to somehow control this?

 

[dietmar]

There is no way to manage this via PMG cluster?

no

Isn't it possible to somehow control this?

no, not within PMG (either sender or receiver need to take care of that).