I have recently been preparing to migrate my accounts running on other mail systems to Bongo as soon as we have Bongo 1.
The movement of mail from any system to Bongo was my biggest worry as my account alone had 3700+ emails in 350+ folders.
I decided after a lengthy web search to use IMAP to migrate the mail.
I will detail the steps I used here so others can expand and use them.
I wanted something I could set-up and run from a script but also it should be able to migrate accounts with multiple folders. After searching myself silly on the net I found imapsync (http://www.linux-france.org/prj/imapsync/dist/)
It was an easy to use solution.
You need to make sure that perl module IMAPClient.pm is installed as it is needed
I used the following command to synchronise just my account
imapsync –host1 imap.domian.com –user1 FirstUser –passfile1 /etc/secret1 –host2 imap.destdomain.com –user2 max –passfile2 /etc/secret2 –noauthmd5
This took about 40minutes on my work link and about 1.5 hours on my poor ADSL link at home.
imapsync moved all my mail and created all the folders. The nice thing is that you could set this up before and the regularly sync the accounts until you are ready to move your domain to the new server.
The imapsync documentation is a bit vague but if you run ./imapsync from the directory that you extracted the files to it will give you explanations that are easier to understand. imapsync has more features than what I used and I am sure that when we start migrating in anger we will use more of them.
I hope this is informative