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

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!