Question : Exchange/GroupWise Encryption

How do you send encrypted messages between GroupWise and Exchange 5.5 recipients ?

Answer : Exchange/GroupWise Encryption

See if some of these answer you're question.

This article describes what happens when a user with 64-bit encryption tries to send a messages to other users, some of whom have 64-bit encryption and others have 40-bit encryption.

http://support.microsoft.com/support/kb/articles/Q181/9/21.ASP?LNG=ENG&SA=ALLKB&FR=0

Seeing as how MS supports the migration from Novell and Groupwise I would think that this acticle applies. MS Outlook is going to encrypt it's messages no matter who it sends them to.

This FAQ addresses the differences between high and low encryption, the types of encryption available in the various Microsoft messaging products, and other issues that are often asked regarding encryption in Microsoft messaging technologies.

http://support.microsoft.com/support/kb/articles/q197/9/65.asp?LNG=ENG&SA=ALLKB&FR=0

Microsoft Exchange Server supports three encryption algorithms: CAST-64, DES, and CAST-40. The level of encryption is determined by the Exchange and/or Outlook client, not the server.
When you are using a CAST-64 or DES client, Exchange sends the message based on the encryption information in the mailbox or individual mailboxes that it is sending to. The CAST-64 and DES clients can read all encrypted mail.
When you are using a CAST-40 client, the directory for that mailbox is updated so that other users will send only 40-bit encryption. While you are logged on to the CAST-40 client, you can not read messages encrypted with CAST-64 or DES encryption.

http://support.microsoft.com/support/kb/articles/Q184/2/26.ASP?LNG=ENG&SA=ALLKB&FR=0