Here is the situation: SolidCP 1.2.1 with Exchange 2016.
User has created contant firstname.lastname@example.org
User creates a full mailbox with same email email@example.com
User will be created but it will NOT get the email address, just the ‘generic” one and custom attributes will be blank
You are correct on this not working.
There’s a few side notes to remember though:
SolidCP creates firstname.lastname@example.org for every contact in exchange.
Exchange it self will not allow any duplicates in this regard (contacts/ mailboxes etc).
However one thing SolidCP should atleast fix up is to alert people clearly that it already exists (and not attempt to create it anyways).