[RCU] Dovecot vs Courier/Others

Kyle Wheeler kyle-roundcube at memoryhole.net
Wed Jul 1 00:56:41 CEST 2009

On Thursday, June 25 at 10:33 AM, quoth Mark Little:
> I know this isn't strictly related to RC only, however I was 
> wondering if I could get some feedback from anyone who has converted 
> from using something like Courier to Dovecot and how you have found 
> the performance differences etc.

I converted from using IMAPProxy+BincIMAP to IMAPProxy+Dovecot, and 
then shortly thereafter I ditched IMAPProxy.

I used BincIMAP originally because it was brain-dead simple to 
configure, and fit well into my authentication mechanism (I used a 
checkpasswd frontend to LDAP) and my mail storage (Maildir). However, 
it was *really* slow at times---particularly when doing any sort of 
server-side searching or sorting. That's why I started using 
IMAPProxy, which helped, but not much. But, silly me, I figured that 
was just how it was, that the speed couldn't be helped, and that Binc 
was as good as any other. I only migrated because Binc was abandoned 
by its developer.

When I moved to dovecot (back in their 1.0rc50 days), I was blown away 
by how fast it was. It indexes, it caches commonly-accessed headers, 
it does everything it can to make IMAP blazing fast. And boy is it 
ever! It was so fast that I tried ditching IMAPProxy altogether, and 
whaddya know, it didn't make a lick's worth of difference in the 
speed. So, out went IMAPProxy.

Since then, Dovecot's just gotten faster. It's got full-text indexing 
now (which it didn't at the time I started using it), and it's 
dramatically improved its caching behaviors too.

And on top of that, Dovecot obeys the IMAP spec more strictly than 
most other IMAP servers 
(http://www.imapwiki.org/ImapTest/ServerStatus), including UW-IMAP. 
Trust me when I say: give Dovecot a try. You won't regret it.

> I have also been looking at IMAPProxy - Does anyone use this with 
> RC? (and Dovecot ?)  Any issues or things I should be aware of?

You can use it... but I don't think it helps much with Dovecot. 
IMAPProxy helps when making new connections is inefficient; but at the 
expense of making MORE connections. This can help if your IMAP server 
is slow to authenticate or slow to open new connections. In my 
experience, the biggest benefit from IMAPProxy was authentication 
speed. Often with webmail, the same user authenticates over and over 
again, and if your authentication method is particularly slow (Binc's 
was), using IMAPProxy saves a lot of time because it caches that kind 
of thing. But if your IMAP server is very efficient at handling 
multiple connections---and Dovecot IS---then IMAPProxy is unnecessary, 
and only serves to make your setup a little more complicated.

Hope that helps,

Beauty is in the eye of the beholder and it may be necessary from time 
to time to give a stupid or misinformed beholder a black eye.
                                                          -- Miss Piggy
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