Controlling mailbox and message size in postfix


Here is today’s incident. Interesting one. So thought of sharing it.

Its related to postfix mail server. I hope you still remember how to configure a basix postfix mail server from your RHCE Certification Training. Got a call from some student. He had configuring postfix in his company and the mailserver was working perfect.

Then today, when someone in the company has tried to send email attachment of size bigger than 9 MB. The mail bounced back. After a bit of honest troubleshooting, at his level. He called me.

I asked him to check limits on mailbox and message. And make them zero, if he is not sure about the limits. After 15 minutes he called again and said, “its still not working”.

I requested him again to please check the limits on mailbox and message. He told me that he had done everything and still the mail is not able to deliver. After a lot of call center like stuff on phone. He was able to find out that he had only changed the – mailbox_size_limit and not the message_size_limit.


Please remember, these are two different things.

mailbox_size_limit – controls the total size of mailbox, including all the emails.

message_size_limit – controls the maximum size of a individual email.

Here is a snapshot for your reference.

Postfix message and mailbox size control

Postfix message and mailbox size control