Defer email via LMTP when there is 'no space left on device' instead of rejecting it

[Will Yardley]

On Sun, Aug 10, 2014 at 06:24:47PM +0200, Luuk wrote:
> On 10-8-2014 06:18, Will Yardley wrote:
> > Depends on the environment; in many cases, the admin could, or may even
> > be expected to, raise the quota.
> 
> !but should not!
> 
> Quota should be set according to some rules, and never be raised because 
> of a 'quota reached'.
 
A few things on this:

1) "Should" is a matter of opinion, and different environments have
different business requirements. I've worked as a sysadmin for almost 15
years, in a variety of different settings (small startup, larger
startup, later acquired by a corporation, academic), and I've found that
there's always *some* squeaky wheel who is going to make a lot of noise
and get their quota raised. In several roles, in fact, that person is
often another technical person, who also happened to be my boss. In
fact, I've been in plenty of situations where quotas can't be set at
all, or are set so high that they're basically useless. I thought (at
times) that changing to a different setting, for example, education,
might change this, but I have not found this to be the case.

In a pure ISP / hosting provider type situation, it is often necessary
to have a strict policy about quotas; however, on the corporate side of
that same organization, there are often different business requirements.

So, if you enjoy the cozy situation of being able to tell your users
what quota they can have, in all circumstances, more power to you, but I
don't think this is typical in the "real world". And, in a sense, it
needen't always be. If more disk space is what whoever the most
important users in your organization "need" to get their work done in a
way that's comfortable for them, it may well be the case that this is
exactly what you'll need to provide for them -- especially if the
organization is willing to fund the hardware necessary to support larger
quotas for some, or all, users.

2) Again, even if the quota policy is strict, it's not always the case
that users understand the error message they get, even if their MUA
presents it in a friendly way.

3) In many cases, users aren't able to delete mail to get under their
(hard) quota without having the quota raised temporarily. If their mail
client deletes by copying messages into the trash, then purging, for
example, I've seen cases where the only way for the user to trim down
their usage is to temporarily increase the quota long enough for them to
get their usage down.

4) Some environments (and some users) require a more "high touch"
approach than others.

> What is the use of 'quota' if the admin raises your quota when things 
> are full?

One use is to prevent a mail loop or other problem affecting one or two
users from filling up a storage volume. Another is so that usage
requirements (and exceptions to default quotas) can be tracked.

Regardless of how individual organizations handles quotas, I don't see
how having Dovecot log an over quota event would be a bad thing.

w