Large imap server.

Bill Campbell freebsd at
Wed Feb 8 15:18:52 PST 2006

On Wed, Feb 08, 2006, Albert Shih wrote:
> Le 07/02/2006 à 16:26:42-0800, Bill Campbell a écrit
>> On Tue, Feb 07, 2006, Albert Shih wrote:
>> >Hi all
>> >
>> >I search some advice for large imap server.
>> >
>> >For me large is : 1000 users with 1 Go mails for each users. And every
>> >users check by imap/pop those mail every 2 or 3 minutes.
>> >
>> >What's the «best» imap server ? Cyrus Imap or Courier-Imap ? (please this
>> >is not a troll).
>> I prefer Courier-imap because it uses Maildir storage while Cyrus
>> uses something similar in that it stores each message in a file,
>> but Cyrus also maintains index files which can get corrupted.
>> We have several systems running courier-imap with 6000+ mailboxes
>> on a single server without problems.
>Lots of thanks for you answer but what kind of server (hardware) you have ?

Pretty standard Intel machines ranging from 1GhZ Pentium IIIs on
up.  The major factor is whether you're planning on running
spamassassin on incoming mail.

SA is a huge memory hog.  

One of our regional ISP customers with just under 10,000 mail
users has one machine that receives all incoming mail, runing
postfix, amavisd-new, and clamav to trap incoming worms and
phishing attacks.  It uses several DNSRBLs and postfix checking
features to minimize the amount of incoming spam.

The load average on this box averages about 0.35.

Mail that's accepted is then forwarded to one of four machines
that then deliver mail to the user's mailboxes, and also provide
POP and IMAP services to any of the users.  These machines are
running single 2.65GhZ Celeraons with 1GB of RAM, and their load
average is around 2.5, rarely getting higher than 4.0.  These
machines use ldap authentication, and the user's home directories
are NFS mounted to the main server.

The hostnames for internal mail delivery, and for pop/imap
services have multiple IP addresses pointing to the delivery
servers which provides simple load balancing.

INTERNET:   bill at Celestial.COM  Bill Campbell; Celestial Software LLC
URL:  PO Box 820; 6641 E. Mercer Way
FAX:            (206) 232-9186  Mercer Island, WA 98040-0820; (206) 236-1676

``Now if there is one thing that we do worse than any other nation, it is
try and manage somebody else's affairs.''
    Will Rogers

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