The route `/mail/unfollow` is used by the button
`Unfollow` in the mail notification template so a user
can remove himself from the followers of a thread.
To be able to remove yourself from the followers,
you need to have the write access on the thread
(see `message_unsubscribe` in `mail/mail_tread.py`)
which you perhaps do not have, for instance if you
are a portal user.
The unsubscribe of this follower from the thread
should therefore be done as sudo.
opw-659295
Denis Ledoux
5e51dc9924