how to migrate mail from argosoft to postfix/dovecot

Any ideas on what a migration strategy might be to sanely migrate mail away from the Argosoft mail server for windows? product site: http://www.argosoft.com/RootPages/MailServer/Default.aspx (note: not the .net version). We are wanting to migrate to a more standard setup using Postfix/Dovecot on Ubuntu.

Would something like imapsync do the trick? Anyone successfully migrate their mail away from the Argosoft Mail Server product?

From serverfault faultyserver

• Using a tool like that will get the mail moved for you, though you should do some testing to see how fast all of your mail can be migrated. What sort of downtime are your users willing to accept while everything is moved over?

  We bring in new e-mail clients all the time and move their existing mail into our system using a similar, proprietary, tool designed to work with our e-mail platform.

  One thing to watch for is if you have a web-based e-mail system with any other information stored in it (address book, calendars, etc.) then you will want to consider those as well for your migration. There's nothing like an angry boss who had all of his contacts in webmail and suddenly can't get to them on the new system.

  faultyserver : Good point, the address book is going to be an interesting item (more than likely a nice difficult proprietary mess) to migrate over. Thankfully we dont have to worry about calendars, planners, other misc 'features' to migrate, the argosoft webmail client is pretty spartan in that regard.
  From Justin Scott