New Calendar Request not displaying correctly

[izumi]

When I get a new calendar request E-mail, it's displays incorrectly. It has html code showing. Other E-mail reminders with links display correctly. Please tell me what's going on, and how I fix this?

Example of E-mail:
-------------------------------------------------------------------------------------
New Calendar Request:

<div class="cal_title">
Dummy1
</div>

<div>
Dummy1 calendar:

Created to see if this function may be used to satisfy various tracking activities:

- Sub-site activities
- Vacations
- etc.

</div>


<a href="http://dev-sbc-11.slb.cal.boeing.com/export_management/plans-bin/plans.pl?active_tab=2&add_edit_cal_action=view_pending">View calendars waiting for approval.</a>
-------------------------------------------------------------------------------------


I have version 7.5.5 installed, on a Windows 2000 IIS server, with Perl 5.6.1.