Set Postfix and Dovecot mail server to store emails as 'vmail:vmail' user group
This is the way I configured it and it works for me:
On postfix master.cf file, add at the end:
dovecot unix - n n - - pipe
flags=DRhu user=vmail:vmail argv=/usr/libexec/dovecot/dovecot-lda -f ${sender} -d ${user}@${nexthop}
On dovecot/conf.d/10-master.conf configure service auth on the following way:
service auth {
unix_listener auth-userdb {
mode = 0666
user = vmail
group = vmail
}
Hope it works for you. Regards