If the following error message appears in mail.log:

fatal: main.cf configuration error: virtual_mailbox_limit is smaller than message_size_limit

it is a misconfiguration.

In the file

/etc/postfix/main.cf

file, the following entry must be added:

virtual_mailbox_limit = 0

After restarting Postfix, the problem should be solved:

$ /etc/init.d/postfix restart