Invitation mails
iCalendar allows to add attendees to an event. The attendee receives a special invitation email.
There are basically three ways to send this mail.
Invitation sent by server
Many servers support sending invitation mails. This is the preferred way because the server is able to manage invitations and answers. The server can update the event's status when receiving an answer from an attendee and directly insert it into the calendars of internal attendees. Also, mail configuration is necessary only once.
Invitation sent by calendar user agent
There are also calendar apps that support invitation mails. Great advantage: The invitation can be sent with a custom text.
Invitation sent by sync adapter
There are two possibilities of implementing emailing into the sync adapter.
- Sending the mails directly via SMTP. That would mean to built in an SMTP client and an IMAP client (to put the mails into the sent folder) and thus additional configuration effort for each account on each device.
- An alternative is to call an android mail app to send the mails manually. Unfortunately it is not easy to forward the necessary headers properly and most mail apps don't support this special kind of mails at all.
Second problem is that since CalDAV-Sync is running in the background and syncing periodically, it is not active at the moment you create an event. So the mail app would pop up at the next sync.
