If the user is a mailing list, this file must exist inside the user account subdirectory and contain a list of users subscribed to this list. The file format is:
"user"[TAB]"perms"[NEWLINE]
where:
subscriber email address.
subscriber permissions:
read.
write (check done using the 'MAIL FROM:<...>' SMTP return path).
write (check done using the email address used for SMTP authentication).
Example:
"axmsuser@mailserver.org" "RW" "ghostuser@nightmare.net" "R" "meawmeaw@kitty.cat" "RA"
If the 'USER.TAB' file defines the 'ClosedML' variable as '1' then a client can post to this mailing list only if it's listed in 'MLUSERS.TAB' with RW permissions.