[Dovecot] acl_shared_dict Format for text files

[Mario Antonio]

If using just a text file for Shared Mailbox Listing, How is the format 
of that file?

acl_shared_dict = file:/vmail/%d/shared.txt

Is this the format for shared.txt?:

fromuser1 at doamin.com  touser2 at domain.com 1
fromuser3 at doamin.com  touser4 at domain.com 1


Regards,

Mario Antonio