Re: using shared mail folders in MIX

On Mon, 12 Apr 2010, Mark Crispin wrote:

> On Mon, 12 Apr 2010, Andrew Daviel wrote:
>> - question: if using the MIX format, what happens to the ownership and
>> permissions of new folder fragments (whatever .mixnnn files are called)
>> in shared folders ? Do they get set with mode 600 hence become unreadable
>> by other group members ?
>
> Mailboxes in #shared are created with mode 660 for files and 770 for
> directories.

I created a group writable folder viz.
drwxr-xr-x  6 imapshared imapshared /home/imapshared/
drwxrwx---  4 imapshared CCN  /home/imapshared/CCN
drwxrwx---  2 imapshared CCN  /home/imapshared/CCN/INBOX/
-rw-rw----  1 imapshared CCN  /home/imapshared/CCN/INBOX/.mix4bc4ef04

An email account "sharetest" which is a member of CCN can deliver mail to 
it using  "dmail +#shared/CCN/INBOX"
and members of the group CCN can read it. So far so good.

However, if a member of CCN "andrew" writes a lot of messages into
this folder using IMAP, the next datafile is created belonging to
him, viz.
-rw-rw----  1 andrew andrew /home/imapshared/CCN/INBOX/.mix4bc51158
Subsequent messages cannot be delivered from dmail, because the file is 
no longer writable.

If the delivery account "sharetest" has group "sharetest" (Linux 
default), new datafiles are created with ownership "sharetest.sharetest" 
and mode 660, so that other group members cannot read them.

If the delivery account "sharetest" has group "CCN",
new datafiles are created with ownership "sharetest.CCN" mode 660
and can be read by group members.

It seems that if I am careful with groups and modes I can have
a number of independant shared accounts.
But if a user needs to be a member of more than one group, there is a 
problem if they write to the shared folder.
If they don't do that, but just read and delete messages, it might be OK

If I use the old Unix scheme where everyone's default group is "users", 
it would work OK but everyone can read all the shared folders.