[MSDN Library April 2000] Optional Features for Address Book Providers (100%)

MSDN Library - April 2000 > Platform SDK > Messaging and Collaboration Services > Messaging API (MAPI) > Guide > Developing an Address Book Provider

[MSDN Library April 2000] Optional Features Transport Providers Can Implement (80.1120448179272%)

MSDN Library - April 2000 > Platform SDK > Messaging and Collaboration Services > Messaging API (MAPI) > Guide > Developing a Transport Provider

[MSDN Library April 2000] Optional Features of ACM Drivers (29.8766233766234%)

MSDN Library - April 2000 > DDK Documentation > Windows 95 DDK > Windows 95 Documentation > Design Guide > Multimedia Device Drivers > Audio Compression Manager Drivers

[MSDN Library April 2000] Optional Messages for Waveform Input Drivers (24.25%)

MSDN Library - April 2000 > DDK Documentation > Windows 95 DDK > Windows 95 Documentation > Design Guide > Multimedia Device Drivers > Audio Device Drivers > Waveform Input Driver Messages

[MSDN Library April 2000] Optional Report Message Properties (22.8956098249576%)

MSDN Library - April 2000 > Platform SDK > Messaging and Collaboration Services > Messaging API (MAPI) > Guide > MAPI Programming Basics > Messages > About Message Properties