Converting mailboxes -- that is, the actual messages and other data -- for use with a different application can be somewhat involved and is best performed with the help of a third party tool. The following migration tools support a large number of popular clients (except AOL):
Moves email, address book and favorites to Outlook or Outlook Express. Requires the AOL email to be installed, does not work with webmail. Supports Windows Vista.
If you need to import your e-mail and address book to other
applications and they support importing from Outlook Express or
Outlook, use ePreserver to convert from AOL, then use the Import
function to import from Outlook or Outlook Express.
Eudora, Netscape and other Internet mail programs
Personal Folders
Microsoft Outlook has built-in support for importing Eudora mail. In Outlook, use File | Import and Export | Import
Internet Mail and Addresses.
Microsoft also has an article on how to import mail from Netscape 4.5 and later:
Personal Folders or Microsoft
Exchange Server mailbox
From Outlook Express, choose File | Export | Messages
(If you have the original version of Exchange distributed
to Windows 95, you must install the Windows
Messaging update first.)
Microsoft Mail
Personal Folders
From Exchange, choose File
| Import and point to your .mmf file.
If HP OpenMail data is stored in users' Personal Folders .pst files, use MailMover for Outlook PSTs (was PSTConverter) to convert all the OpenMail addresses using an address map that you specify.
Personal
Folders or Microsoft Exchange Server Mailbox
Microsoft Mail
Create a Microsoft Mail shared
folder, then drag all the Exchange messages to it. When
you connect via MS Mail, drag all the messages from the
shared folder to your personal Microsoft Mail folders.
Outlook Personal Storage files (*.pst),
Outlook MSG files (*.msg), Outlook Express, EML message files (*.eml),
MHT Web Archive files (*.mht),
Mozilla (including Netscape and Thunderbird),
Generic mailbox files (mbox, Berkeley, BSD, Unix), Eudora, PocoMail,
Opera, Forte Agent,
The Bat!, Pegasus, Calypso and Courier, PMMail message files (*.msg),
FoxMail, maildir folders,
Mailbag Assistant, E-mail Examiner and Aid4Mail ZIP archives.
Outlook Personal Storage files (*.pst), EML message files (*.eml), MHT Web Archive files (*.mht), Mozilla (including Netscape and Thunderbird), Generic mailbox files (mbox, Berkeley, BSD,
Unix, PocoMail, Aid4Mail ZIP archives.