For the Outlook Express folders try DbxConv. This is a utility which is
designed to convert Mail (not news) folders from Outlook Express DBX
folders to standard MBX files importable by almost any mail program.
Pegasus Mail can read these *.MBX files directly, you simply point at the
directory containing the MBX files using the "Add mailbox to list".
http://people.freenet.de/ukrebs/dbxconv.html
For the Outlook folder there is a utility called PM2MSN32.exe from Martin
Ireland that can convert the Outlook folders to Pegasus Mail message files.
PM2MSM32 is a specialized 32bit Mapi client that interfaces directly with
Microsoft MsExchange/Outlook (or any other Mapi mail server). It extracts
the content of the InBox to individual text files that can be imported to other
mail systems such as Pegasus Mail. In the case of Pegasus Mail it puts
CNM files into the new mail directory and then you can put these into a
separate folder. http://www3.telus.net/public/irelam/
For Eudora or Netscape MBX type folders you can use "Add mailbox to list to
point at the directory containing the *.MBX files. You can also use Mail
System Converter to convert to and from a these and a few other mail
programs. http://www.interguru.com/mailconv.htm or the latest version is
always available from http://www.dragon-it.co.uk/pegasus.htm
For the address books use Dawn, created by Boris Zakharin
Dawn works with the following programs:
* Becky!
* Corel WordPerfect Address Book 8.x
* Eudora
* ExecMail / Simeon
* Internet Explorer / Outlook Express / Windows Address Book (WAB)
* Juno 2.0 - 5.0
* Mozilla
* Netscape 3.0 - 7.0
* MS Outlook 98 / 2000 / 2002 -- Outlook 97 not supported
* Opera
* Palm support through Palm Desktop (read only)
* Pegasus Mail
* Pine (PC and UNIX) -- Mailing Lists not supported
* Other programs which can use/import/export LDAP/LDIF, vCard (VCF),
Comma Separated Value (CSV), plain text, one per line or comma separated
formats or store addresses in a text file suitable for extraction
http://mysite.verizon.net/zakharin/software/Dawn/
And finally, if cost is not a problem, there is also the commercial program
UniAccess for $49 for 1 user. http://www.comaxis.com/ua.htm
UniAccess is a Windows 9x/NT utility for converting between a variety of
"legacy" and leading edge e-mail systems. Now you can migrate your users
without leaving behind their valuable messaging archives.
The features of UniAccess include:
Source systems: Exchange, Outlook, Notes, Netscape, Eudora, Pegasus
Mail, MHS, ExpressIT, GroupWise, cc:Mail (archives and folders), daVinci e-
Mail, Notework, Compuserve.
Target systems: Exchange, Outlook, Notes, Netscape, Eudora, Pegasus
Mail, MHS, ExpressIT, GroupWise, HTML, generic.
Convert multiple file or folder sets in one operation
Optionally convert messages based on search criteria
Optionally limit distribution list and attachment size
Batch mode for mass, unattended migrations
Convert address books
For the Outlook Express folders try DbxConv. This is a utility which is
designed to convert Mail (not news) folders from Outlook Express DBX
folders to standard MBX files importable by almost any mail program.  
Pegasus Mail can read these *.MBX files directly, you simply point at the
directory containing the MBX files using the "Add mailbox to list".
http://people.freenet.de/ukrebs/dbxconv.html
For the Outlook folder there is a utility called PM2MSN32.exe from Martin
Ireland that can convert the Outlook folders to Pegasus Mail message files.   
PM2MSM32 is a specialized 32bit Mapi client that interfaces directly with
Microsoft MsExchange/Outlook (or any other Mapi mail server).  It extracts
the content of the InBox to individual text files that can be imported to other
mail systems such as Pegasus Mail.  In the case of Pegasus Mail it puts
CNM files into the new mail directory and then you can put these into a
separate folder.  http://www3.telus.net/public/irelam/
For Eudora or Netscape MBX type folders you can use "Add mailbox to list to
point at the directory containing the *.MBX files.  You can also use Mail
System Converter to convert to and from a these and a few other mail
programs. http://www.interguru.com/mailconv.htm or the latest version is
always available from http://www.dragon-it.co.uk/pegasus.htm  
For the address books use Dawn, created by Boris Zakharin
Dawn works with the following programs:
* Becky!     
* Corel WordPerfect Address Book 8.x    
* Eudora
* ExecMail / Simeon
* Internet Explorer / Outlook Express / Windows Address Book (WAB)
* Juno 2.0 - 5.0        
* Mozilla
* Netscape 3.0 - 7.0  
* MS Outlook 98 / 2000 / 2002 -- Outlook 97 not supported
* Opera
* Palm support through Palm Desktop (read only)    
* Pegasus Mail     
* Pine (PC and UNIX) -- Mailing Lists not supported
* Other programs which can use/import/export LDAP/LDIF, vCard (VCF),
Comma Separated Value (CSV), plain text, one per line or comma separated
formats or store addresses in a text file suitable for extraction
http://mysite.verizon.net/zakharin/software/Dawn/
And finally, if cost is not a problem, there is also the commercial program
UniAccess for $49 for 1 user. http://www.comaxis.com/ua.htm
UniAccess is a Windows 9x/NT utility for converting between a variety of
"legacy" and leading edge e-mail systems. Now you can migrate your users
without leaving behind their valuable messaging archives.  
The features of UniAccess include:
Source systems: Exchange, Outlook, Notes, Netscape, Eudora, Pegasus
Mail, MHS, ExpressIT, GroupWise, cc:Mail (archives and folders), daVinci e-
Mail, Notework, Compuserve.  
Target systems: Exchange, Outlook, Notes, Netscape, Eudora, Pegasus
Mail, MHS, ExpressIT, GroupWise, HTML, generic.  
Convert multiple file or folder sets in one operation  
Optionally convert messages based on search criteria  
Optionally limit distribution list and attachment size  
Batch mode for mass, unattended migrations  
Convert address books