[Dovecot] Well, "Hard filesystem quota can also be problematic"

Jeroen Scheerder Jeroen.Scheerder at phil.uu.nl
Tue Aug 16 09:16:57 EEST 2005

Curtis Maloney wrote:
> Stewart Dean wrote:
>> We do...otherwise, there's the inevitable 'Tragedy of the 
>> Commons'...to say nothing of idiots mailing MB files to everybody in 
>> the community. And we're still on UW IMAP and the one-big-file INBOX 
>> which is a horror show when it gets big.
> I also run Dovecot on a box with filesystem quotas, but just like Alan 
> Premselaar, I also use Maildir.  When people have hit their quota, 
> there's been no evidence of lost mail, as Postfix simply refuses the 
> message.

This is a non sequitur.  Mail storage is more than just the inbox.

Postfix does honour its "mailbox_size_limit", true.  But there's more to store 
than just a single mailbox, of which the maximum size can be set to enforce 
quota, in some or other way.

Or am I misunderstanding, and does Postfix (or procmail, which is typically 
used as Postfix' local delivery agent) have explicit quota handling that I've 
been overlooking?

Perhaps you mean to say that a write error occurs upon hitting hard quota, or 
upon exceeding the grace period after a soft quotum has been surpassed, and 
that the local delivery agent seems to handle this gracefully.

That may be true.  However, I think this fact alone, although it lets one 
sleep better, is not sufficient.  Dovecot especially may require even more 
storage after delivery.  Furthermore, mail delivery isn't the only way 
mailboxes get modified: the IMAP server also needs to, and to make it really 
work it seems necessary for the IMAP server to report filesystem quota to the 
IMAP clients.

Apparently, v4 of the IMAP protocol has a QUOTA extension for this; it's 
reported as a CAPABILITY.  I think some of that is documented in [1].  Am I 
wrong in suspecting that this is a higly desirable, or even a required, piece 
of the puzzle?

-- J$

[1] <http://www.melnikov.ca/mel/Drafts/draft-cridland-imap-quota-00.txt>

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