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. Excessively small values will result in the loss of non-delivery notifications, when a bounce message size exceeds the local or remote MTA’s message size limit. Continue reading “Allow large attachment (greater than 10MB) in ISPConfig postfix MTA” »