Does anyone allow unlimited or extremely large quotas?

Kenneth Marshall ktm at
Tue Nov 16 10:35:05 EST 2010

On Tue, Nov 16, 2010 at 08:41:46PM +0530, Shuvam Misra wrote:
> > > I think the issue you will encounter first is clients will start to fall
> > > down when folders exceed a 'reasonable' number of messages.  Common IMAP
> > > clients I've seen start to exhibit severe performance issues beyond a
> > > few hundred thousand messages.
> > 
> > As far as I'm aware (the helpdesk guys know better than me so I'm parroting
> > their reply), Outlook 2003's PST file has a limit of 2GB so if it's locally
> > caching folders, you may run into that.
> > 
> > If you use Outlook 2007 or later, the limit is more like 20GB.  BUT, if you
> > upgrade from 2003 and use the same PST, that PST may continue with the same
> > 2GB limit.  Apparently you might need to create a new PST file and move the
> > mail into it?.  Some big users have been moved to Thunderbird to avoid this
> > and to improve performance.
> > 
> > Gavin
> > 
> > ? To be honest, I haven't personally dealt with this issue, but this
> >   paraphrases the knowledge of those here who have.  I'd think of it as
> >   having "[citation required]" beside it.
> I'm in an almost-identical position w.r.t. lack of direct knowledge, but
> our Support guys say exactly the same things about Outlook 2003 and
> Outlook 2007 and size limits of PST files.
> That said, we have users of our product who have 40GB mailboxes.
> Cyrus works perfectly happily with all this. The problem is the number
> of messages in the current folder, as many have mentioned before me. We
> keep telling users to clean up their Inboxes and keep a max of 1,000
> msgs there. We know things will be fine with 10,000 messages too, but
> 100,000 msgs in a folder is pushing things.
> We find that Webmail chokes server performance much earlier than normal
> IMAP clients do. I know this has nothing to do with Cyrus, but I just
> thought I'd mention it. Most programming environments in which such
> Webmail thingies are written (mostly PHP on the server and nowadays
> lots of Javascript on the browser) cannot keep an IMAP connection to the
> Cyrus server open between pages, therefore each time a user clicks on a
> folder or does any other operation, there's this fresh IMAP connection
> and a huge surge of IMAP operations while the folder contents are listed
> afresh, etc. This puts a lot of load on the server. I guess Webmail is
> OT on a Cyrus mailing list, but can't help asking: any suggestions for
> improving Webmail performance? (Admission: we haven't yet tried imapproxy
> -- it appears to be a good piece of C which will help things.)
> regards,
> Shuvam

We use imapproxy here to avoid exactly this situation with webmail.


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