On Thu, 9 Jun 2016, Andre Felipe Machado via Info-cyrus wrote:

Bron Gondwana via Info-cyrus <info-cyrus@lists.andrew.cmu.edu> wrote ..
On Thu, Jun 9, 2016, at 03:02, Andre Felipe Machado via Info-cyrus wrote:
Hello,
At future release notes I read
"Under delete_mode: delayed, only the 20 most recently deleted mailboxes are
kept for any given name."
https://cyrusimap.org/imap/release-notes/3.0/x/3.0.0-beta2.html
Is there any configuration parameter to increase this limit?
Why this limit is needed?

denial of service / space wastage protection.  There's no config option 
available
right now.  I could be convinced to change it.

How would you suggest we protect against exploiting delayed delete to fill the
server without going over quota?  Maybe a new quota field for "total mailbox 
usage
including deleted stuff" that can be set to a high enough value that no 
reasonable
user will ever hit it?

Bron.

--
  Bron Gondwana
  br...@fastmail.fm
----

Hello, Bron
I understand the problem.
But at a corporate scenario, it is a rare event, because of jobs at stake, 
tracked user accounts,  antispam measures, etc.
It is more likely a "rogue" client,  bug/misconfiguration on a smartphone 
causing such problems.
We stay with official debian repositories versions as long as we could, 
receiving security patches.
So, mantaining an unofficial patch will be a big problem.
The sysadmin configurable parameters will be a more elegant solution.
Having configurations at sysadmin control will mantain cyrus flexible for use 
at different usage scenarios.
For the DoS / waste space problems, the 2 quota limits configurations are more 
suitable than counting folders quantity.
What if each folder contains 1 TB deleted messages?
Maybe a reasonable default (10 times user quota?) for those not wanting to 
configure is good idea.
Even better to have also a way to control individual accounts total quotas, for those 
corporate accounts like "sa...@foo.bar" that  receive lots of legitimate emails 
and have to
delete them after processing.
We have zabbix monitoring space at our cyrus backends, and need unlimited  or 
configurable delayed expunge limits for recovering messages and folders for 
years at corporate
scenario.
Thanks .
Andre Felipe

Remember, this is a limit on the number of deleted *mailboxes* kept, not messages.

Bron, this could impact Pine/Alpine users that frequently postpone messages. Pine creates a folder named "postponed-msgs" to store drafts. The folder is created when a draft is saved and deleted when all drafts have been deleted/sent.

Here is my personal deleted folders list, right now:

DELETED.user.morgan.postponed-msgs.5755CF0C     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F446     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F486     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F4D1     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F4E4     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F50E     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F65F     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5755F844     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5756ECFC     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.5756F602     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.575706F8     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.57585C5D     0 p2 morgan     lrswipkxtecda
DELETED.user.morgan.postponed-msgs.57587FE1     0 p2 morgan     lrswipkxtecda

We are removing deleted mailboxes after 7 days:

delprune      cmd="/usr/local/cyrus/bin/cyr_expire -E 1 -X 7 -D 7" at=0100


I don't know if other IMAP clients have similar quirky behavior, but I could see myself running into this limit. However, I certainly don't care about recovering my old postponed-msgs mailboxes.

Hmmm, is this a limit per-mailbox (user.morgan.postponed-msgs) or per-user (all mailboxes under user.morgan)?

Thanks,
        Andy
----
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