Allow large attachment (greater than 10MB) in ISPConfig postfix MTA Rumi, March 4, 2018 Just a small hack, but worked good on my ISPConfig 3 setup. Add the following: nano /etc/postfix/main.cf mailbox_size_limit = 104857600 Save and restart postfix service. According to official postfix documentation: message_size_limit (default: 10240000) The maximal size in bytes of a message, including envelope information. Note: be careful when making changes…. Continue Reading