[Dovecot] Postfix aliases with quota-status service

[/dev/rob0]

On Tue, Aug 06, 2013 at 09:27:20PM +0300, Timo Sirainen wrote:
> On 6.8.2013, at 20.57, Thomas Leuxner <tlx at leuxner.net> wrote:
> > * Timo Sirainen <tss at iki.fi> 2013.08.06 19:42:
> > 
> >> The idea behind quota_grace is that the last mail would be 
> >> allowed to take the user somewhat over quota (e.g. up to 109% 
> >> quota usage). On the next mail delivery user is already over 
> >> quota, so the size of the mail is irrelevant because a mail
> >> of any size will be rejected. The initial quota-status 
> >> implementation didn't even support SIZE extension since I
> >> didn't remember it existed.
> > 
> > I'm referring to the Postfix side _only_ or the initial SMTP 
> > Handshake if you like. My point is that there is no safe way
> > to reject mails at this level *if* the remote server doesn't
> > play nice. I think this was the whole point of writing a
> > policy service for Postfix. I'm not *talking* about quotas
> > that will be handled by the delivery agents...
> 
> Either you're still misunderstanding me, or vice versa. The quota 
> rejections can be done complete in SMTP side even without SIZE:

Another way, in Postfix, is to wait for end-of-DATA. Regardless of 
SIZE being given, at that point, the actual size is known.

Of course as Thomas would probably point out, such a rejection is 
unsafe, because ANY overquota recipient would cause rejection for 
EVERY recipient; SMTP cannot have per-recipient results except at 
"RCPT TO:".

Personally, I'd much rather allow the last overquota mail, even in 
cases where the user goes far over the quota. Apparently Thomas 
intends to have a solid, inflexible quota.

In that case I'd suggest going for a lower quota and adding 
quota_grace. Let quota_grace plus quota be the most you can tolerate 
in your users' mailboxes.

> 1) quota at 99% :
> 
> MAIL FROM:<sender at example.com>
> 250 2.1.0 Ok
> RCPT TO:<tss at dovecot.org>
> 250 2.1.0 Ok
> DATA
> ...
> .
> 250 2.0.0 Ok: queued as 12345
> 
> 2) quota is now at 103% :
> 
> MAIL FROM:<sender2 at example.com>
> 250 2.1.0 Ok
> RCPT TO:<tss at dovecot.org>
> 554 5.2.2 User is over quota
> 

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