PHP Mail Error "not supported calendar message.ics" iCal - php

Question

I'm sending this ical as part of a multi/part email message. However I'm getting an error in outlook "not supported calendar message.ics" I have confirmed I have both a Attendee and an Organizer so I dont know why this would be happening.
$ical = 'BEGIN:VCALENDAR' . "\r\n" .
'PRODID:-//Microsoft Corporation//Outlook 10.0 MIMEDIR//EN' . "\r\n" .
'VERSION:2.0' . "\r\n" .
'METHOD:REQUEST' . "\r\n" .
'BEGIN:VTIMEZONE' . "\r\n" .
'TZID:Central Time' . "\r\n" .
'BEGIN:STANDARD' . "\r\n" .
'DTSTART:20141101T020000' . "\r\n" .
'RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=1SU;BYMONTH=11' . "\r\n" .
'END:STANDARD' . "\r\n" .
'BEGIN:DAYLIGHT' . "\r\n" .
'DTSTART:20090301T020000' . "\r\n" .
'RRULE:FREQ=YEARLY;INTERVAL=1;BYDAY=2SU;BYMONTH=3' . "\r\n" .
'TZOFFSETFROM:-0500' . "\r\n" .
'TZOFFSETTO:-0400' . "\r\n" .
'TZNAME:EDST' . "\r\n" .
'END:DAYLIGHT' . "\r\n" .
'END:VTIMEZONE' . "\r\n" .
'BEGIN:VEVENT' . "\r\n" .
'ORGANIZER;CN="'.$rep.'":MAILTO:'.$repemail. "\r\n" .
'ATTENDEE;CN="'.$to_name.'";ROLE=REQ-PARTICIPANT;RSVP=TRUE:MAILTO:'.$to_address. "\r\n" .
'LAST-MODIFIED:' . date("Ymd\TGis") . "\r\n" .
'UID:'.date("Ymd\TGis", strtotime($startTime)).rand()."#".$domain."\r\n" .
'DTSTAMP:'.date("Ymd\TGis"). "\r\n" .
'DTSTART;TZID="Central Time":'.date("Ymd\THis", strtotime($startTime)). "\r\n" .
'DTEND;TZID="Central Time":'.date("Ymd\THis", strtotime($endTime)). "\r\n" .
'TRANSP:OPAQUE'. "\r\n" .
'SEQUENCE:1'. "\r\n" .
'DESCRIPTION: '.$description. "\r\n" .
'SUMMARY:' . $subject . "\r\n" .
'LOCATION:' . $location . "\r\n" .
'CLASS:PUBLIC'. "\r\n" .
'PRIORITY:5'. "\r\n" .
'BEGIN:VALARM' . "\r\n" .
'TRIGGER:-PT15M' . "\r\n" .
'ACTION:DISPLAY' . "\r\n" .
'DESCRIPTION:Reminder' . "\r\n" .
'END:VALARM' . "\r\n" .
'END:VEVENT'. "\r\n" .
'END:VCALENDAR'. "\r\n";
// Send Appointment .ical file
$message .= 'Content-Type: text/calendar;name="message.ics";method=REQUEST\n';
$message .= "Content-Transfer-Encoding: 8bit\n\n";
$message .= $ical;

Answer 1

You're dealing with the outlook sniffer, the task that processes invitations on arrival. It's ridiculously picky and there's no documentation. Start by checking your Icalendar in the online validators. Then, send an invitation from gmail to Outlook. Use Gmail "show original" to inspect the generated Icalendar. Change your application to match exactly the gmail invitation, including the order of fields, and you should find your invitation is correctly processed by Outlook.