I have courier running as a backend for webmail app for more than 400,000 users without a problem. You will find imap is not the biggest problem, I found the slowest thing was the webmail application itself.

As it is webmail, you won't find a lot of imap sessions running (as you would with a normal imap session/client). It connects does what it needs to do and disconnects.

Because of this I run it across 6 machines with a load balancers in front of them using network attached stoeage for data store. (Courier hasn't caused me many issues over NFS unlike other (I won't name them) imap servers).

If you don't need it, I would turn off imap keywords, I notice some performance improvements. There is various notes in the distrubtion config file also about performance gains if you turn off some features (expecially if your webmail doesn't support it).

As I said, webmail is more likely to be a bottle neck then anything else (even with optimised setups) when compared with imap.

Ricky

Hans du Plooy wrote: