I have built a new server (FreeBSD-12) running dovecot-2.3.4.

My old server (FreeBSD-9.3) is running dovecot-2.3.4 as well.

The configurations are 1:1 identical.

The are about 250 users on this server, all virtual. They are mostly POP3 users, but they do "leave a copy of message on the server"

for set various number of days.

Now, to migrate the mail data, can I simply rsync the mail directories between the old and the new server? Would that create a pitfall??

What is the recommended method?