does fedora have anything requiring :mail rw access?

[Michal Hlavinka]

Hi all!

I've got quite simple question from dovecot's upstream: Why do we have rw 
access on mails for mail group? Why /var/mail/<username> files have 0660 
<username>:mail permissions instead of 0600 permissions? The fact is, I don't 
know the answer and I'd appreciate your help.

Some facts:

distro   | group | perm
---------+-------+---------
Fedora   | mail  | 0660
Ubuntu   | mail  | 0600
openSuSE | users | 0600 (user is member of users group)
debian 4.0 | mail | 0660

(Note: This is result of my own investigations on installed systems or 
livecds, I don't know if any installed system had changed settings.)

Interesting thing is, that when new user is added to the system, useradd 
creates /var/mail/<username> file with <username>:mail 0660 permissions, but 
when you delete this file and the user gets new email, this file will be 
autocreated with 0600 permissions (still <username>:group owned) and it seems 
everything still works.

useradd command comes from shadow-utils and fedora contains no patch changing 
permissions to 0660.

The most important question is: Is there anything that requires these files can 
be read and written by mail group? 

If you have any info regarding this, please share.

Thanks,
Michal Hlavinka