Courier to Dovecot and folder subscriptions

[nino]

Hi,

First, I'm sorry if this questions have already been answered before, but I just have to be extra sure before doing anything on my server.

We have a server suffering from overloads and I believe it's related to Courier Imap. When the loads goes up (sometimes above 150) I see lot's of processes related to imap. The courier imapd itself, lots of "php-cgi" called from webmaild and so.

Many people suggests that we change the imap server from Courier to Dovecot. The problem is that most of our users, if not all of them, uses folders subscriptions and there lies my questions.

Question 1 - If I change the option on cPanel to use Dovecot will it convert the folder subscriptions or will I get my phone ringing with customers asking "Where's my folder"?

Courier uses a file called "courierimapsubscribed" inside each mail foder. Will cPanel convert this file to Dovecots format? Which I don't know how it is our how it works...

Question 2 - If cPanel does not care about converting anything and just changes the "imap authenticator", what will happen to these Courier files? "courierimapsubscribed" and the folders will be wiped out?

Question 3 - What exactly does cPanel do when we change these options?

Thanks.

 

[nino]

Forgot to mention, I'm using "WHM 11.36.1 (build 6)" on a "REDHAT Enterprise 6.4 x86_64 standard"

 

[Infopro]

On the Mailserver selection page in WHM:
WHM » Service Configuration » Mailserver Selection

It states this:

Convert mailbox settings file format to new mail server's format during migration

When checked, the settings files for each mailbox will be converted into the format for the new mail server. This includes information about read messages, mailbox subscriptions, etc. Unchecking this box will cause your clients to lose their mailbox settings but will speed up the migration.