"Logins with UID 0 not permitted" and "User user is missing userdb info"

If you see the following errors in your /var/log/maillog, it likely means that your /etc/virtual/domain.com/passwd file has not been updated to the dovecot format.  The passwd file, with dovecot, requires 7 columns, colon separated.  If you only see 2, then your passwd file hasn't been converted.

Sep  1 22:42:34 s1 dovecot[3869]: user [email protected]: Logins with UID 0 not permitted
Sep  1 22:43:10 s1 dovecot[3869]: auth(default): passwd-file /etc/virtual/domain.com/passwd: User user is missing userdb info

To resolve this issue, first ensure that you have:

dovecot=1

present in your /usr/local/directadmin/conf/directadmin.conf.

Next, run the following:

cd /usr/local/directadmin/custombuild
./build todovecot
/etc/init.d/directadmin restart

(If you're using freebsd, the directadmin restart is:
"/usr/local/etc/rc.d/directadmin restart")