[Dovecot] DC testing observation and a question

[Jack Stewart]

Scott Silva wrote:
> on 1-9-2009 10:16 AM Stewart Dean spake the following:
>>
>> 1) Watching the syslog maillog has been intriguing...different IMAP
>> client show widely differently use patterns.
>> a) Users running TBird and Seamonkey have 2-5 imap sessions (ps -aef |
>> grep <userid>) *but* very little syslog activity...sparse occasional
>> logins and disconnects
>> b) Users running Exchange have only 1 imap sessions *but* every 5
>> minutes will generate login and disconnect messages (in and out in the
>> space of a second) for each folders.  So for a user with 22 folders,
>> there will be 44 syslog messages in the maillog every 5 minutes.
>> Just curious....any thought as to which is more efficient and by how much?
>>
>> 2) When I try to switch a MacMail client over, it sees the new mail, but
>> not the old mail in the INBOX.  How do I  force re-indexing on the test
>> server?
> By Exchange to you mean Outlook?
> 
> Outlook's (and Outlook Express) have poorly written IMAP implementations IMHO.
> Outlook is first and foremost a client for an Exchange server, with somewhat
> decent POP3 support. OE is just the POP3 and buggy IMAP.
> Later versions added HTML support mainly to access hotmail.
> 
> They both seem to poll each folder for info instead of using IMAP calls.
> 

First with question #2, it isn't clear to me if you need to have the 
INDEX cache or dovecot-uidlist file rebuilt. Try removing one or the 
other with a test account and see what happens (start with INDEX first). 
If it is one or the other, the simplest thing might be to change the 
location of these files in your configuration file for the new server. 
Of course this will impact all of the clients (forcing them to rebuild 
their indexes). For your sake, I hope it is just the INDEX files.

Here is what I know (or at least think I know), on some various E-mail 
clients that should help to explain what you are seeing in the log 
files. It can useful it getting your customers to have the appropriate 
configuration for their client.

Thunderbird/Seamonkey use IMAP IDLE when possible and often use one 
connection per monitored folder.

Depending on the version and configuration for Outlook/Outlook 
Express/Entourage, you often get a periodic full synchronization polling 
where the client checks the header of each message in the folder against 
its internal index. This is even if it supports IDLE and is using IDLE 
on the INBOX. I have seen older versions of Outlook Express open an IMAP 
connection for every folder (subscribed or not) when simultaneously when 
syncing (i.e. 10 folders, 10 connections).

More recent versions of MacMail likes to keep a full copy of every 
messages including attachments in all subscribed folders. This is so it 
can use spotlight.

A blackberry uses IDLE but, if you use more than one client at the same 
time, RIM suggests that you may wish to have the administrator turn off 
IDLE or have your blackberry to use POP. I am not kidding on this one. 
We have a blackberry user where we found this change necessary.

Mutt and pine are mostly behave, but it is worth changing their default 
settings in order to tune down the poll interval. rmail over stunnel has 
more problems with postfix than it does with dovecot.


So I recommend to our users that they check for new mail no more 
frequently than once every five minutes (once every ten minutes for 
MacMail). My excuse is that they don't want to stomp on their 
synchronization(s). They seem to buy this explanation. I check the log 
files every so often and give users who check for new mail every minute 
or less a stern finger wagging.

Hope this helps.

---Jack