If you're talking Exchange 2003 and below, Exmerge
will do the job for the users with Outlook PSTs. For those using Web Access, you could either use Outlook to download the mail to PSTs or use IMAPSize to directly transfer the mail between IMAP servers (assuming you've enabled IMAP on your Exchange server). For Exchange 2007, Exmerge is not officially supported but has been known to work.
Re: Export/Import mail from ISP's server to Exchange 2007
11 years 3 weeks ago #23039