[Dovecot] dovecot with postfifx with 200 users in /etc/passwd as local user

hi for all, someone have any experiencie with dovecot and postfix with 200 users in /etc/passwd as local user? is a funcionatly, or have some errors in the future?, and how the users can change they passwords?, now for change passowrd I have to use the #passwd usuerx and to add a user # adduser, the populars commando, please some recomendation?