UPGRADING TO LOTUS NOTES 6 AND LOTUS DOMINO 6
Using calendar and scheduling features with Internet mail
In an environment that routes mail over Notes RPC and SMTP, the Domino router automatically routes meeting invitations, appointments, and other calendar and scheduling information over Notes RPC when possible. When mail is routed over SMTP -- for example, if you send a meeting invitation to someone over the Internet -- calendar and scheduling items are converted to text messages. Notes RPC is required to use the workflow features in Notes calendar and scheduling items.

Note Conversion of calendar and scheduling items to text when routing over SMTP works the same way in Lotus Notes 6 as it did in Lotus Notes 4.6 and Lotus Notes 5.