After modifying base_calendar.py to send e-mails as wanted by users, another question which is in our minds if it is possible to accept an invitation directly via e-mail? Same functionality is used in Google calendar (which below all attendees has links to confirm or reject invitation) and I wish it could be added to our installation. I guess there is no problem for creating a hyperlink to calendar, but I found it difficult to link to exact related id record with focus on invitations tab with edit meeting form. Any ideas how to approach that?