Setting Up of IMAP Server

[Greg A. Woods]

At Fri, 11 Dec 2009 18:30:47 +0530, prasanna <prasannap at cdac.in> wrote:
Subject: Setting Up of IMAP Server
> 
> Some of my requirements are
> 
>     1) Users are created using /etc/passwd, No Mysql or LDAP at present. 

As others have mentioned the easiest solution overall in this case it to
use the autocreate patches for Cyrus IMAPd such that Postfix becomes
authoritative on which mailboxes exist and so will properly reject
undeliverable mail during the initial SMTP transaction, and yet messages
for newly created users will be accepted by Postfix immediately and
their new INBOX folder will be created when immediately and
automatically when Postfix delivers the first message to their INBOX.

>     2) User should be given quota for their INBOX, selected users should 
>     have unlimited or variable quota

"variable quota" is an oxymoron, i.e. an antinomy, a self-contradiction.  :-)

With Cyrus IMAPd you can set a mailbox quota to some value, you can
change it to a different value, and you can set it to "none" (to allow
"unlimited" quota, which means allow the mailbox to fill the filesystem).


>     3) Quota exceeded users mails should be stored somewhere other than 
>     their inbox, on request from the user should be delivered to them by 
>     increasing their quota for time being.

Do you want them to have a quota, or do you not want them to have a
quota.  What is the purpose of the quota?  If the purpose of the quota
is to prevent users from utilizing more than some pre-determined, fixed,
quantity of _system_ resources, then you MUST enforce the quota
uniformly throughout the entire system.  This means rejecting e-mails
when the user's mailbox size has reached or exceeded its quota limit.

If you allow, say, Postfix, to queue messages when the user's mailbox is
at-or-over-quota then you have not prevented that user from utilizing
more system resources than they have been allocated.  I.e. you may as
well not define any mailbox size quota for them AT ALL.  It is
pointless and confusing.

Worst of all senders will have no idea that their mail has not yet been
delivered (unless/until it finally is bounced by Postfix after the
maximum queue lifetime has been reached).

If you want to implement quotas then you really need to enforce them
uniformly and firmly throughout the entire system, as otherwise they
will only result in confusion.

>     4) Web based Management of User. 

With the autocreate patch this is mostly no longer a problem that can or
should be dealt with by the mail system.

What might remain is management of mailbox quotas, assuming you do
really want to implement quotas, and perhaps dealing with mailboxes for
deleted users and other sundry cleanup details.

>     5) Backup option of user mailbox  should be available. 

Backups are effectively a system level issue, not a direct issue to be
dealt with explicitly by any given application.

-- 
						Greg A. Woods

+1 416 218-0098                VE3TCP          RoboHack <woods at robohack.ca>
Planix, Inc. <woods at planix.com>      Secrets of the Weird <woods at weird.com>