Mail size to big


One of my clients is receiving this error when trying to receive a large email, do you know where can adjust the config to allow bigger emails to be received?

Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 552 552 5.3.4 Error: message file too big (state 18).


this can be adjusted by postfix configuration.
consult postfix docs and adjust your /etc/postfix/ accordingly.
write here if you can find a solution, or not.

I have looked in the postfix config, I'm supposed to change this line:

message_size_limit (default: 10240000)

But there is no such line in my config file.

I guess, you can append a line with that, like