I've run into a little problem lately, the mailbox of my internal mx filled up and filled its maximum of 50MB. To make changes to your mailbox, you will have to adjust the maximum allowed size. this can be done by the following changes: [archy@mx01 ~]$ sudo vim /etc/postfix/main.cf and insert the line mailbox_size_limit = 0 # for no limit at all, not recommended! mailbox_size_limit = 104857600 # 100MB in bytes save and close the file. You now have to restart postfix in order to reread the config file. To restart, run [archy@mx01 ~]$ sudo systemctl restart postfix.service The mailbox will now be allowed to reach 100MB in size at maximum. Feel free to comment and / or sugguest a topic.