Send email to Outlook with ics meeting appointment

Question

I want to send an email with appointment\meeting (ICS) to Outlook client. When the user receive the email he should accept the meeting invitation and automatically the meeting goes to the calendar and the email is automatically deleted.

I'm using this code:

public void Sendmail_With_IcsAttachment()
{

    MailMessage msg = new MailMessage();
    //Now we have to set the value to Mail message properties

    //Note Please change it to correct mail-id to use this in your application
    msg.From = new MailAddress("[email protected]", "ABC");
    msg.To.Add(new MailAddress("[email protected]", "BCD"));
    msg.CC.Add(new MailAddress("[email protected]", "DEF"));// it is optional, only if required
    msg.Subject = "Send mail with ICS file as an Attachment";
    msg.Body = "Please Attend the meeting with this schedule";

    // Now Contruct the ICS file using string builder
    StringBuilder str = new StringBuilder();
    str.AppendLine("BEGIN:VCALENDAR");
    str.AppendLine("PRODID:-//Schedule a Meeting");
    str.AppendLine("VERSION:2.0");
    str.AppendLine("METHOD:REQUEST");
    str.AppendLine("BEGIN:VEVENT");
    str.AppendLine(string.Format("DTSTART:{0:yyyyMMddTHHmmssZ}", DateTime.Now.AddMinutes(+330)));
    str.AppendLine(string.Format("DTSTAMP:{0:yyyyMMddTHHmmssZ}", DateTime.UtcNow));
    str.AppendLine(string.Format("DTEND:{0:yyyyMMddTHHmmssZ}", DateTime.Now.AddMinutes(+660)));
    str.AppendLine("LOCATION: " + this.Location);
    str.AppendLine(string.Format("UID:{0}", Guid.NewGuid()));
    str.AppendLine(string.Format("DESCRIPTION:{0}", msg.Body));
    str.AppendLine(string.Format("X-ALT-DESC;FMTTYPE=text/html:{0}", msg.Body));
    str.AppendLine(string.Format("SUMMARY:{0}", msg.Subject));
    str.AppendLine(string.Format("ORGANIZER:MAILTO:{0}", msg.From.Address));

    str.AppendLine(string.Format("ATTENDEE;CN=\"{0}\";RSVP=TRUE:mailto:{1}", msg.To[0].DisplayName, msg.To[0].Address));

    str.AppendLine("BEGIN:VALARM");
    str.AppendLine("TRIGGER:-PT15M");
    str.AppendLine("ACTION:DISPLAY");
    str.AppendLine("DESCRIPTION:Reminder");
    str.AppendLine("END:VALARM");
    str.AppendLine("END:VEVENT");
    str.AppendLine("END:VCALENDAR");

    //Now sending a mail with attachment ICS file.                     
    System.Net.Mail.SmtpClient smtpclient = new System.Net.Mail.SmtpClient();
    smtpclient.Host = "localhost"; //-------this has to given the Mailserver IP

    smtpclient.Credentials = System.Net.CredentialCache.DefaultNetworkCredentials;

    System.Net.Mime.ContentType contype = new System.Net.Mime.ContentType("text/calendar");
    contype.Parameters.Add("method", "REQUEST"); 
    contype.Parameters.Add("name", "Meeting.ics");
    AlternateView avCal = AlternateView.CreateAlternateViewFromString(str.ToString(), contype);
    msg.AlternateViews.Add(avCal);
    smtpclient.Send(msg); 
}

The mail is correctly sent but in outlook (I'm testing it with outlook 2010) it shows the body, location,data, and it shows the calendar but above the calendar in the mail I see "Impossible to find the meeting on the calendar" and the "Accept","Decline"" buttons are disabled!

I have tried other solutions and found on the web for ex. DDAY.Ical but I haven't found any example to use it.

FYI, both your MailMessage and SmtpClient need to be in using blocks: using (MailMessage msg = new MailMessage()){... using (SmtpClient smtpClient = new SmtpClient()){ ... smtpClient.Send(msg);}} — John Saunders
Whether it's the issue or not, you should do that - I've seen mail not be delivered for 2 minutes, until the garbage collector got around to cleaning up. — John Saunders
Could you add the full resulting MIME message to your post ? — Arnaud Quillaud

Franky Franky · Accepted Answer · 2015-03-20T12:37:33

After a lot of digging i found the solution:

You need to set the content-class of your eMail to

Content-class: urn:content-classes:calendarmessage

so add this to your code and it should work

msg.Headers.Add("Content-class", "urn:content-classes:calendarmessage");

Send email to Outlook with ics meeting appointment

2 Answers