[imp] setting newmail checking default.

[Lord Apollyon]

> we are having a problem with our imap servers getting swamped by our imp
> 
> server.  I'd like to set the newmail checking to every 5 minutes by 
> default.  Is there a way to do this? 

You can change your site code to do this.  Of course, you probably cannot
(safely) disable "manual" mailbox reloads/refreshes.

I suspect you'd do well to use an IMAP proxy - that would save you alot of
connection tear-down and tear-up costs.  Also, do *NOT* use tcp wrappers,
but rather, employ firewalling settings to limit inbound imap connection
access (if you use such access limiters at all). tcpd adds some non-trivial
overheads which become significant at your loadings.

Also, have you changed your inetd.conf settings for the imapd service to
handle the connection loads?  Stock inetd.conf settings assume a 256
connection/minute level before backing off new connections as a "flood"
control measure.  You can change this by appending ".512" or whatever
connection/minute level you wish to support after the "nowait" parametre.

Your line would look like this (assuming your path to imapd is
/usr/sbin/imapd) and that you wanted to lift the connection/minute limit to 512:

imap2   stream  tcp     nowait.512  root    /usr/sbin/imapd  imapd

Other tips:

1) *DO* run PHP-Accelerator - the performance delta for me was 4-5X.

2) Look into experimenting with the preemptible-kernel patch which has been
rock-solid stable for over a year now.

ftp://ftp.kernel.org/pub/linux/kernel/people/rml/preempt-kernel/v2.4/

I use it on most of my servers because even when the loads get high, the
responsiveness to network and system events smoothly "degenerates" rather
than getting burpy/laggy (this is alot more noticeable with SSH sessions
mind you).  Maybe my overall system throughput is slightly less as a result
(OS theory would tell you this), but all of my users FEEL like the system is
more responsive.   I will leave you to judge which is the more important.

3) At your loading levels, investigate one of the two imap-proxies - it WILL
make a difference to not have to re-authenticate and rescan mailbox files.

> the Zend php accellerator at this time but may. 

Get it.  It will both reduce your system loadings and improve page render
speeds.

Also, try to spray your mailbox spool files across multiple spindles.  All
of the OS tricks and CPU speeds in the world won't get you far if you're
bottlenecking at a single hard disk.

All of the ancient mainframe tuning tricks apply to these "modern OSs", folks.

=Apollyon=