From: DeskNow Knowledge Base
http://www.desknow.com/kb/

How can I migrate accounts and emails from another mail server (ex. Exchange) to DeskNow?
http://www.desknow.com/kb/idx/9/128/article/

It is possible to automatically migrate accounts and emails from any IMAP server into DeskNow.

The migration process is fully automated and described in the Administration manual, at the section 'User administration/Importing accounts and emails from another mail server'

Please note that this process is available only in DeskNow 3.1 and later.

It is also possible to import accounts and emails selectively form another server, by using the built-in DeskNow Administration API. This is useful if only some accounts need to be imported, if mail is to be imported into existing accounts, etc.

To import mail from external IMAP accounts using this method, see the administration manual at the section 'Administration API/Import mail from a remote IMAP account' . You can also use the bulk administration tool (available at http://www.desknow.com/tools.html) to import mail accounts in a batch operation, from an simple spreadsheet. Tip: for a single user, try opening this URL in a browser:

http://www.yourdesknowserver.com/desknow/admin?pwd=adminpassword&action=mail_importimapaccount&username=desknowusername&domain=desknowdomain.com&host=mail.oldmailserver.com&remoteusername=oldusername&remotepassword=password

 

This process is available in DeskNow 3.0 and later.