How to get ics calendar invitation to automatically add to calendar - outlook

Question

I am generating .ics calendar invitation with the node package ical-generator and sending the attachment in an email via mandrill.
The .ics calendar invite contains information for one event at a specific time and date.
example generated file:
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//sebbo.net//ical-generator//EN
METHOD:REQUEST
NAME: xxxx Events
X-WR-CALNAME: xxxxx
BEGIN:VEVENT
UID:5wzd#xxx.com
SEQUENCE:0
DTSTAMP:20180318T202459Z
DTSTART:20180330T230000Z
DTEND:20180330T230000Z
SUMMARY:test
LOCATION:test
DESCRIPTION:test
ORGANIZER;CN="info":mailto:info#xxxx.com
END:VEVENT
END:VCALENDAR
Right now, the user receives the calendar invitation as an attachment in the email and is able to add the event to their calendar if they open up the attachment and click on "add to calendar" (in outlook).
What changes do I need to make so that the calendar invite is automatically parsed by the mail client and added to the user's calendar (similar functionality is found in email confirmation from sites like meetup and eventbrite).
Not sure I have the context knowledge around how email clients, calendar systems or .ics files work to have a framework of how to approach this problem
Any suggestions or pointers to resources is greatly appreciated! Thank you!

Answer 1

You need to consider three points in order to add events automatically:
Email Header
iCalendar Method
ATTENDEE information the "VEVENT" calendar component
Email Header
In order to get the email client to parse correctly the attached .ics file, you should add the scheduling method and MIME information to the email headers. This is specified by the iCalendar Message-Based Interoperability Protocol (RFC 2447).
For this reason, your header should include Content-Type,
Content-Transfer-Encoding and Content-Disposition as specified in the following example:
Content-Type: text/calendar; charset=utf-8; method=REQUEST; name=invite.ics'
Content-Transfer-Encoding: Base64
Content-Disposition: attachment; filename=invite.ics
iCalendar Method
When used in a MIME message entity, the value of "METHOD" must be the same as the Content-Type "method". This can only appear once within the iCalendar object. The value of this field is defined by the iCalendar Transport-Independent Interoperability Protocol (iTIP) (RFC 5546).
In order to request for a meeting, the value should be "REQUEST".
METHOD:REQUEST
ATTENDEE information the "VEVENT" calendar component
This property is the state of a particular "Attendee" relative to an event. It is used for scheduling and is defined by the "PARTSTAT" parameter in the "ATTENDEE" property for each attendee.
ATTENDEE;PARTSTAT=ACCEPTED;CN="Jane
Doe";EMAIL=jdoe#gmail.com:MAILTO:jdoe#gmailcom
Here is an example of a minimal .ics file:
BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
METHOD:REQUEST
BEGIN:VEVENT
UID:<unique-id>#<site>.com
DTSTAMP:20210605T073803Z
DTSTART;TZID=America/Guayaquil:20210614T030000
DTEND;TZID=America/Guayaquil:20210614T040000
SUMMARY:My Event
ORGANIZER;CN="Juan Perez":mailto:jperez#organizer.com
ATTENDEE;PARTSTAT=ACCEPTED;CN="Jane
Doe";EMAIL=jdoe#gmail.com:MAILTO:jdoe#gmailcom
URL;VALUE=URI:https://<site>.com/event/5960492994476830083
END:VEVENT
END:VCALENDAR
For more details, please take a look at my gist.

Answer 2

You need two things to get this working:
1) The correct encoding of the attachment in your email, see this email headers:
Content-Disposition: attachment;
filename=meeting.ics
Content-class: urn:content-classes:calendarmessage
Content-Type: text/calendar;
name="meeting.ics";
component="VEVENT"
Content-Transfer-Encoding: 7bit
2) The correct format for the ics file. If you work in PHP to generate the ICS file you should use the library provided from icalendar.org
Try to use this event to test if working and use the validator present in the site mentioned above.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ZContent.net//ZapCalLib 1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
SUMMARY:Simple Event
DTSTART:20200101T120000
DTEND:20200101T130000
UID:2020-02-12-11-02-23#demo.icalendar.org
DTSTAMP:20200212T100223
Description:This is a simple event\, using the Zap Calendar PHP library. Vi
sit http://icalendar.org to validate icalendar files.
END:VEVENT
END:VCALENDAR

Answer 3

The best you can do is ensure that the ics file is well setup, with the text/calendar header etc.
The providing system cannot force on the users device how the file is dealt with, it is entirely within the control of the receiver and their device setup.
For example I have my windows pc set to open ics files in a text editor, while my iphone will try to do an add to calendar (the icloud one), but I actually use google calendar. And Gmail used to not automatically add invites unless they'd been sent to the gmail address, whereas I use other domains for personal/family vs work, which all go to gmail. I'm not sure whether that is still a problem. I don't want the auto added.
Depending on the sort of system you developing for, You might want to consider having the recipients subscribe once to a personal ics url, rather than sending individual invites all the time. If subscribed, then future events/classes etc will automatically show up. I love it when systems do that, but too often they don't. EG: classes that one signs up individually for.