CODEWITHSUNDEEP
c#outlookicalendarmime
Marc
Marc

Reputation: 13194

Construct MIME message for outlook compatible meeting invitation

I am failing to construct a MIME message that is displayed as a meeting invitation in Outlook, compared to when sending an invitation natively via Outlook.

What I want is this view (at least more or less):

alternative view

What I get instead:

fail

(The file displayed as .ics attachment can be opened and shows correct content).

Here's the meeting body (ics), that I construc programmatically:

BEGIN:VCALENDAR
VERSION:2.0
PRODID:123
CALSCALE:GREGORIAN
METHOD:REQUEST
BEGIN:VTIMEZONE
TZID:Europe/Amsterdam
BEGIN:STANDARD
TZOFFSETTO:+0100
TZOFFSETFROM:+0100
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Europe/Amsterdam:20201214T085500
DTEND;TZID=Europe/Amsterdam:20201214T095500
SUMMARY:Test Event
LOCATION:skico HQ
DESCRIPTION:A test in appointment chatbot
PRIORITY:3
END:VEVENT
END:VCALENDAR

The MIME message is built via MimeKit:

private static string BuildMimeContent(Mail mail)
    {
        
        var textBody = new TextPart("plain") { Text = mail.BodyText };
        var htmlBody = new TextPart("html") { Text = mail.BodyHtml };

        var alternative = new Multipart("alternative");
        alternative.Add(textBody);
        alternative.Add(htmlBody);

        var multiPart = new Multipart("mixed") { alternative };

        if (mail.Event != null)
        {
            var eventBody = mail.Event.Parse();

            var calendarBody = new TextPart("calendar")
            {
                Text = eventBody,
                ContentTransferEncoding = ContentEncoding.Base64
            };
            
            calendarBody.ContentType.Parameters.Add("method", "REQUEST");
            calendarBody.ContentType.Parameters.Add("name", "meeting.ics");
            alternative.Add(calendarBody);              
           
        }
       
        var mimeMessage = new MimeMessage();
        mimeMessage.From.Add(new MailboxAddress(mail.Sender.Name, mail.Sender.EMail));
        mimeMessage.To.Add(new MailboxAddress(mail.Recipient.Name, mail.Recipient.EMail));
        mimeMessage.Subject = mail.Subject;
        mimeMessage.Body = multiPart;

        // parse and return mime message
        return mimeMessage.ToString();
    }

yielding:

MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="=-rdfmBTE1TuDNFI0Wzfmibg=="

--=-rdfmBTE1TuDNFI0Wzfmibg==
Content-Type: multipart/alternative; boundary="=-6bp3YWbl6STSnwQq7Fne2A=="

--=-6bp3YWbl6STSnwQq7Fne2A==
Content-Type: text/plain; charset=utf-8

Hi!
--=-6bp3YWbl6STSnwQq7Fne2A==
Content-Type: text/html; charset=utf-8

<strong>Hi!</strong>
--=-6bp3YWbl6STSnwQq7Fne2A==
Content-Type: text/calendar; charset=utf-8; method=REQUEST
Content-Id: <[email protected]>

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Microsoft Corporation//Outlook 15.0 MIMEDIR//EN
CALSCALE:GREGORIAN
METHOD:REQUEST
BEGIN:VTIMEZONE
TZID:Europe/Amsterdam
BEGIN:STANDARD
TZOFFSETTO:+0100
TZOFFSETFROM:+0100
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Europe/Amsterdam:20201214T120800
DTEND;TZID=Europe/Amsterdam:20201214T130800
SUMMARY:Test Event
LOCATION:skico HQ
DESCRIPTION:A test in appointment chatbot
PRIORITY:3
END:VEVENT
END:VCALENDAR

--=-6bp3YWbl6STSnwQq7Fne2A==--

--=-rdfmBTE1TuDNFI0Wzfmibg==--

How does the MIME content need to be constructed instead, such that the alternate view works in Outlook?

Upvotes: 1

Views: 1570

Answers (1)

Marc
Marc

Reputation: 13194

There was something wrong with my ICS content. This fixed it:

BEGIN:VCALENDAR
PRODID:-//Microsoft Corporation//Outlook 15.0 MIMEDIR//EN
VERSION:2.0
METHOD:REQUEST
BEGIN:VEVENT
DTSTART:20201214T121600Z
DTEND:20201214T131600Z
SEQUENCE:0
UID:56b39b14ebb641ab7de716a62bed46aa
DTSTAMP:20201210T121600Z
LAST-MODIFIED:20201210T121600Z
SUMMARY:Test Event
LOCATION:s HQ
DESCRIPTION:A test in appointment chatbot
END:VEVENT
END:VCALENDAR

I did not track it down to the root cause. Probably the UID is madatory or the date/timezone format was invalid before.

Upvotes: 1

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