When I send an invitation in MS Outlook on the Calendar for an appointment, the person receiving the invitation receives a plain text message of code rather than an appointment that they could have normally just hit "Accept" or "Reject" and that appointment would have normally have been added it the calendar. Now, they only receive an email, not an appointment. Can anyone help?

Are they sure it's not a problem their end? Sounds to me as though perhaps they've changed their settings to plain text instead of html?

Thanks for replying!! I asked them and they haven't changed their settings. Neither have I. When I try sending an appointment to myself, the same thing happens.

As you've done a self-test then we can assume it's you that is the culprit. Have you tried inserting your software disk to repair Outlook?

yes, no luck though. same result.