As a Xink admin, you can assign special signatures to users with access to shared mailboxes and to users that has access to more than one user mailbox.
A mailbox that's not primarily associated with a single user and is generally configured to allow logon access for multiple users.
A mailbox that's assigned to an individual user in your Exchange organization. It typically contains messages, calendar items, contacts, tasks, documents, and other important business data.
You set the shared signatures as optional and assign it to the users(s) - Either individually or via group setting (rules).
Then the user can select the optional signature by right clicking the default (can also select in the Outlook menu).
You select 'Do not change' which means that the user can select his own default/reply and the Xink client will not overwrite.
How to set 'Do not change' individually:
How to set 'Do not change' for groups via rules:
Now the the E-mail account settings are preserved when the Xink client updates: