Webmail application that doesn't abuse the IMAP server?

Gary Mills mills at cc.UManitoba.CA
Tue Jun 10 23:11:31 EDT 2003

On Tue, Jun 10, 2003 at 09:27:13PM -0400, Ken Murchison wrote:
> Gary Mills wrote:
> >Does anyone know of an e-mail web application that doesn't abuse the
> >IMAP server by making short connections?  Most of them simply connect
> >and disconnect with each HTTP transaction.  Is there one that behaves
> >the same as an IMAP client, using one connection for the duration of
> >the session.  An IMAP proxy is not adequate because most of them only
> >cache TCP connections and perhaps authentication.  These are generally
> >not the source of most of the transaction overhead.
> So what part of the connection to you perceive as the most expensive? 
> The selection of the mailbox?  This might be cacheable, but that depends 
> on how the webmail client is written (ie, simply caching it might screw 
> up some of the client's logic).

I haven't determined that.  I suspect, though, that there are limits
to what can be cached by a proxy.  A better design might involve a
persistent portion of the webmail application, that maintains some
state across HTTP transactions.  The communications between the two
portions need not involve IMAP.

> FWIW, Dave McMurtrie's imapproxy (http://www.imapproxy.org/) works quite 
> well with IMP/Cyrus, and is very well written.  It doesn't cache the 
> selected mailbox, but it does keep an authenticated (and optionally 
> encrypted) connection open with the server.

We do use that, and it probably does improve performance.  It does have
a problem with idle browser connections that accumulate with time.
This also ties up a lot of `imapd' and `httpd' processes.  It probably
needs a client timeout someplace.  I haven't had time to investigate

-Gary Mills-    -Unix Support-    -U of M Academic Computing and Networking-

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