Postfix mail server is installed on the Plesk server.
"Maximum Message Size" value specified in Parallels Plesk Panel at Tools & Settings > Mail Server Settings is being changed to 10000 Kb after running
The problem is caused by the error in code.
The problem has been fixed in Parallels Plesk Panel 11.5. Consider upgrading to the latest version.
For previous versions of Parallels Plesk Panel, use the following workaround:
Set the needed value for "Maximum message size" on Tools & Settings > Mail Server Settings.
Login to the server by SSH and check
message_size_limitin Postfix configuration
# grep message_size_limit /etc/postfix/main.cf message_size_limit = 2097152000
mailbox_size_limitvalue in Postfix configuration to the same or greater value:
# postconf -e mailbox_size_limit=409715200
# /etc/init.d/postfix restart