[Dovecot] Could sharing a folder with other users cause a loss of emails?

[Alfred Nutile]

we are trying to figure out how and email box is not empty.
All we did was
/mail/user1
/mail/user2
/mail/shared

ln -s /mail/shared /mail/user1/shared
ln -s /mail/shared /mail/user2/shared

Perms are fine and people where dropping emails in here fine.

We added a third one and the user also right clicked in their IMAP
client and added a subfolder.
It was around that time they where gone.

Could any of these actions cause that?
PS it is not a mbox layout.
Thanks!