Disable user login with uid

[guldendraak at gmx.net]

Hi list
 
as per the Kolab Multi-Domain setup documentation (https://docs.kolab.org/howtos/multi-domain.html), "Cyrus IMAP has, by default, been configured to allow users to login with a uid, mail or alias login username, translating that login username to the intended mailbox using a process called canonification."
 
Is it possible to change this so that users can only log in with their email address or alias and not with their uid?