I am using Outlook 2002, and I have invited someone from
outside my company (also Outlook 2002) to a meeting.

When he opens the invitation, it has converted it to an
email, and so he cannot accept.

Do I have to use the iCal format? If I do, this option is
greyed-out under Tools, Otions, Calendar options, Advanced.

Any help would be really appreceiated.

Thanks,
Rob E.