I have the similar problem, but generating database isn't possible with this command
postmap /etc/postfix/vmail_ssl.map
because I'm getting this:
postmap: warning: /etc/postfix/vmail_ssl.map.db: duplicate entry: "webmail.somedomain.com"
postmap: warning: /etc/postfix/vmail_ssl.map.db: duplicate entry: "mail.somedomain.com"
postmap: warning: /etc/postfix/vmail_ssl.map.db: duplicate entry: "webmail.somedomain2.com"
postmap: warning: /etc/postfix/vmail_ssl.map.db: duplicate entry: "mail.somedomain2.com"
etc...
And it is right, this file vmail_ssl.map has really double entries, but why?
It is generated at night, so I guess there is some bug that is generating double lines.
Is this a bug?