dovecot - Oct 2014 - how to migration exchange'mail to dovecot?

hi :
   i want to migration all users's mails of exchange server to our
dovecot:but  i don't know how to do this ?
   i know that exchange server can put users's mails to file.pst  , but i
don't know hwo to convent file.pst to file.eml .
               please help     thanks !

On October 27, 2014 4:03:01 AM 576709166 <576709166 at qq.com> wrote:
>    i know that exchange server can put users's mails to file.pst  , but
i
>    don't know hwo to convent file.pst to file.eml .
You should stop fokusing on microsoft precompiled problems, if exchange can 
be used in imap protocol then simply use imapsync to get mails synced over 
to new server

Check if your distro have imapsync, else ask how to use dsync with dovecot
> please help     thanks !
users is generic helpfull here without ever write please