Was getting log entries for postfix failures:
“file too large”
“message file too big”
The fix was to run these commands
sudo postconf -e mailbox_size_limit=0
sudo postconf -e message_size_limit=0
sudo postconf -e message_size_limit=0
0 is unlimited
To set to another value enter size in bytes for example 30720000 = around 29M
The default is 10240000 bytes (around 9M)