Do these two share a single user ID, or do they use separate IDs? Think about file/directory ownership and permissions. If user IDs 123 and 234 attempt use the same directory, things will break. User 123 should not be able to delete a file owned by user 234, for example.
yes, same UID/GID because they are infact the same user. What I was hoping to do was to either tell dovecot they are infact the same or mask one of them so dovecot ignored one. I guess that's not possible?
Perhaps have a look at your setup, and verify that you are matching multiple logins to a single OS user ID only. For example, you can use LDAP login to map an arbitrary login name to a given UID. This works nicely with Dovecot.
I am trying to keep things simple. I would rather drop support for the system /etc/passwd file and move every user into the dovecot users file before moving to ldap. My setup would not warrent that.
Dave McGuire had a similar idea of using an SQL stored proc which also probably would have worked but just too complicated for what i'm doing.