Creating an iCal file involves generating a .ics file with the event details. Here's a simple example:
BEGIN:VCALENDAR VERSION:2.0 PRODID:-//Your Organization//Your Product//EN BEGIN:VEVENT UID:uid1@example.com DTSTAMP:20231001T123000Z DTSTART:20231101T090000Z DTEND:20231101T100000Z SUMMARY:Your Event Title DESCRIPTION:Description of the event. LOCATION:Location of the event END:VEVENT END:VCALENDAR
Once you have this file, you can upload it to your server and provide a link to it in your email.