Pois é meu amigo, existe, de facto, alguma incompatibilidade entre os dois, mas tem solução. Tive exactamente o mesmo problema.
Comigo resultou na perfeição, tenho o Win XP home SP2, Outlook 2003 e Winfax Pro 10.01.
A solução passa por aqui:
Section 2: How to disable WinFax 10.02 and Outlook XP integration
To disable integration, close Outlook 2002, and then follow the steps in each of the following sections.
To disable Outlook Integration in WinFax Message Manager
1. Open WinFax Message Manager.
2. Click Tools, and then click Program Setup.
3. Double-click Email and Outlook Integration.
4. Uncheck Enable sending faxes by email.
5. Click OK, and then click Close.
6. Shut down Message Manager and Controller, then restart.
To rename Outlook\WinFax integration files, if they exist
1. Exit all open programs and stop the WinFax PRO service if you are running Windows NT, Windows 2000,
2. Click Start, point to Find, and click Files or Folders. The Find dialog box appears.
3. From the Look In drop-down list, select the drive on which you installed WinFax PRO.
4. Check "Include subfolders" (if not already checked.)
5. In the Named field, type Wfxext.dll and click Find Now. Windows displays all files matching the search
6. Right-click the Wfxext.dll file name, and then click Rename.
7. Change the file name to Wfxext.old and click OK.
8. Repeat the above steps to rename the following files so that the file name extension is .old
Dccmsp32.dll
Dccwfp32.dll
Wfoladin.dll
9. Restart the computer, and test to see whether the problem is fixed.
If the problems persists, uninstall and reinstall WinFax
1. Completely remove WinFax from the system:
To manually uninstall WinFax Basic Edition, see the document How to manually uninstall WinFax B
To manually uninstall WinFax PRO, see the document How to perform a complete removal of WinF
PRO.
2. Restart the computer and install WinFax. When prompted, choose to not integrate Outlook 2002 with Win
3. Complete the installation.
4. Use the "To rename Outlook\WinFax integration files, if they exist" section to find the integration files, an
they have been recreated.
5. Restart the computer.
Espero ter ajudado
