Hi and thanks a lot for this great library!

My feature request: I would like to use Simple Java Mail to send calendar invitations, which have to smoothly integrate with Gmail/Google calendar and MS Outlook but should also get properly displayed in any ordinary client. This means I have to create multipart/alternative messages consisting of 3! alternatives: text/plain, text/html and text/calendar - at least MS Outlook is sending such invitations. Simply adding the ICS as attachment does not work with Outlook.

I found no way how to do this with Simple Java Mail, e.g. there is no setTextVCalendar() or addCustomText(String text, String mimeType).

What do you think?