I've used the following successfully to send an email (that includes bc recipients) via GroupWise.
I 'stuff' the email addresses into strEmails and then the email is address accordingly.
Application.FollowHyperlink "mailto: firstname.lastname@example.org?bcc=" & strEmails
Problem: I now would like to include an attachment with this email. I found many other ways to do so using Outlook object, etc. However, I've tried those methods before arriving at the Application.FollowHyperlink one as I am using GroupWise and need BCC function.