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Subject: Re: pop-before-smtp (was Re: FreeInet and checking mail?)
From: Brad Knowles (blkskynet.be)
Date: Wed Jun 07 2000 - 14:25:39 CDT

At 2:22 PM -0400 2000/6/7, Lawrence Greenfield wrote:

> Our production IMAP server (which you can connect to using anonymous
> IMAP at cyrus.andrew.cmu.edu) served well over 9000 unique logins in
> the last week of the spring semester.

        9000 unique logins? We have over 600,000 mailboxes on one of our
servers, with over 400,000 active accounts. Maybe I don't understand
how you're counting unique logins, but this would seem to me to be a
loss of scalability of about two orders of magnitude.

> Ironically, this _hurts_ scalability. Reestablishing connections,
> reauthenticating users, and reestablishing protocol context is much
> more expensive than a single idle TCP/IP session sending a NOOP every
> 30 minutes.

        The problem is that you have limited numbers of connections that
can remain open at any one point in time. We saw peaks with more
than six thousand users simultaneously logged on several months ago
-- I have no idea what the current numbers are. During that same
period of time, we had peaks of over 2000 total POP3 connections in
various states of being set up, used, or torn down, of which 450-520
were actually established.

        Now, my interpretation of the IMAP protocol is that we would
probably expand this by about a factor of five to ten. I would
challenge you to build a server that could handle that many
simultaneous connections (even if they are mostly idle), and that
many more connections that may be in various stages of being
dismantled.

        We've got an interesting twist on this concept that should allow
us to scale the system more easily, but I'm not at liberty to talk
about the details. Suffice it to say that I think the inbound mail
system is well on its way to being taken care of -- and in a manner
that will be scalable and let us decide when and where we need to
throw more hardware at the problem.

        Now I just have to worry about the outbound, and how I handle
anti-virus scanning for the entire system.

> www.messagingdirect.com Unix based IMAP servers

        I'm familiar with them. They took your code and have hacked on it.

> www.iplanet.com ditto

        I'm familiar with them. I'm not interested in paying them ten
times as much money per mailbox per month as we are currently
charging our partners for our existing POP3 mailboxes. I'm also not
interested in paying them on the order of a dollar per mailbox just
to have it listed in the local iPlanet LDAP directory.

> www.mirapoint.com IMAP appliances, meant to scale horizontally

        I'm familiar with them. They have two installations so far, of
which their largest is ~80k mailboxes. The hardware is slightly
hacked-up FreeBSD 2.x, and the software is slightly hacked-up older
releases of sendmail (some of which is being used in violation of the
licensing terms, etc...).

        These guys are really slimy. Sorry, not interested.

> www.software.com IMAP backed with large Oracle databases

        Most of the carriers I know of that have done business with them
are actively looking for alternative providers, because the software
is about as bad as it could possibly get (until relatively recently,
they couldn't even close the open relay hole), and the service is
less than nonexistant. There are literally billions of dollars to be
made in the business of replacing all current software.com
installations with other systems that actually work.

        There is one more name that you haven't mentioned. Maybe you're
aware of them and maybe not.

        However, because I do not want to sound like a walking
advertising campaign, I also will not mention their name. 

--
   These are my opinions -- not to be taken as official Skynet policy
======================================================================
Brad Knowles, <blkskynet.be>                || Belgacom Skynet SA/NV
Systems Architect, Mail/News/FTP/Proxy Admin || Rue Colonel Bourg, 124
Phone/Fax: +32-2-706.13.11/12.49             || B-1140 Brussels
http://www.skynet.be                         || Belgium