Dear Maintainer,
When using Icedove (45.4.0-1~deb8u1) with Iceowl-extension and a few calendar with active "offline support", Icedove take a very long time to start (several minutes).
I tried to use a new profile but this issue still remain. Disabling iceowl make Icedove works fine, that's why I investigate in this direction. When disabling offline support for all my calendar (one Owncloud caldav calendar, one ICS calendar from my university) Icedove start in a few seconds and all seems to work, including the calendar.
If you need more information, please contact me.
Thank you for your work !