To build open source based scalable, stable webmail server

[Erol Ozcan]

Hi!

  I am looking for a scalable, stable and cost effective webmail
server solutions. The server system

 - should be cost effective and based on open source softwares as
possible ( could be commercial )
 - should be scalable up to 200,000 users, but 150,000 a must
 - account creation or deletion should not exceed 2 seconds
 - could be support concurent 100 subscribers for webmail browsing on
the system without any performance problems 
 - should not be create real system user for mail or other purposes.
Account information stored LDAP or other databases.
 - does not needed pop3 support
 - could ( i think should ) be cluster or similiar system ( load
balance, round robin dns..., MUPDATE )
 - Webmail system should be support basic webmail functionality like
read, compose, mail, delete, folders, address book, able to view
attachments...
 - users quota limit could  be 1 MB or even 256 MB since webmail system is used only for special
mail traffic ( MMS content ).
 - user accounts on the current Suse eMail server could be migratable to the new server. ( I think
i needed write scripts )
 - could be a bit high price hardware solutions ( my customer will
provide hardwares )

  I have looked Suse OpenExchange server, there are too many features
that we dont need such as exchange server integration, projects,
appointment etc. Its not cost effective solution any more due to
client prices.

  I have looked Cyrus Murder configuration but i dont understand differences at the follow. I
think that the system have 203069 users but only 26516 users have been using their mail box, am i
right?

mailboxes (*): 203069
user mailboxes (user.*): 173414
user INBOXes (user.%): 26516

  I urgently need your software/hardware suggestion and/or experience to build new scalable,
stable webmail system.

  - Any ready distribution ? ( like Suse eMail server )
  - Which IMAP server ? ( Cyrus, Courirer or .. )
  - LDAP based or ?
  - Postfix or Qmail?
  - How to scalable, distribute, load balance etc. servers?
  - About Cyrus MUPDATE: currently uses, tutorials, docs.
  - Some example hardware configurations ?
  - Any others...


  By the way, I have many experiences with Linux systems and also Java programming. So do not
hesitate to advice some hacking ( not many or big, because time is very limited ) if it is really
needed.

Thanks in your advance.
Erol

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