I am going through the process of migrating shared mailbox from onprem to o365, and its been giving me nothing but trouble.
regardless of mailbox permissions ie. direct full access, mail enable sec group
before migrating the mailbox the user already has access to it in 2013 world
the following morning after migration to o365, the user has a password prompt when trying to access the shared mailbox
webmail access is no problem
profile rebuild always seems to fix it
i have plenty of these do, and there is no way i am going hand fix these one by one.
client version is outlook 2016 mix of w10 and w7
automapping does work, as the user ends up with 2 profiles, the automapped one, and the one that prompts for password..
not sure what strategy to take with this. any ideas..
PS prior to migration it was added in cached mode
and most of the time removing the passwords from vault, also fixes it post migration.