Every time I log into KDE, Kontact starts up showing contacts tab, and popping up the Akonadi server self-test window, which reports that a previous server error log was found. No matter if I start a blank session, or if I add it to the exclude list: it will always start. Autostart directories are empty. To be honest, ./config/autostart has krunner.desktop and plasma-desktop.desktop files in it, but it looks like they're not relevant to this issue.
This happens since I played around with an LDAP address book, if I remember correctly. Anyway, deleting the LDAP address book doesn't solve the problem.

I'm stuck, since I don't know where else to look to find out why Kontact wants so stubbornly draw my attention, so any help would be really appreciated.

Thanks

The following worked for me when I wanted to avoid Kontact from starting automatically.

I use the exclude from session method, but for some reason it is not sufficient to just give the binary name: you need to give the full path like:

/usr/bin/kontact

Also, verify that other automatically started processes don't need Kontact ( such as KOrganizer Notification Daemon )

Nope, even with /usr/bin/kontact it starts anyway
Also, KOrganizer Notification Daemon - or other daemons that may start a kontact instance - isn't in my startup daemons, nor in load-on-demand ones. Perhaps I'm missing something, so this is the list of my startup daemons:
- Keyboard daemon
- Power management
- DNS-SD
- Removable device automounter
- Nepomuk search module
- Activity manager
- obexftp
- Input actions
- Status notifier manager
- Time zone
- Drive ejector
- BlueDevil
- Free space notifier
- NetworkManager User setting service
- Network status
- Remote URL change notifier
- Display management change monitor

Hope this helps.

Ok, I managed to disable it by disabling KOrganizer Notification Daemon from the system tray.
Thanks!