Problem solved:
Deleting and reimporting of the root and the class 3 certificate helped.
** Changed in: evolution (Ubuntu)
Status: New = Invalid
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Own certificates are marked as not valid
https://bugs.launchpad.net/bugs/447078
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** Attachment added: Dependencies.txt
http://launchpadlibrarian.net/33348152/Dependencies.txt
** Attachment added: ProcMaps.txt
http://launchpadlibrarian.net/33348153/ProcMaps.txt
** Attachment added: ProcStatus.txt
http://launchpadlibrarian.net/33348154/ProcStatus.txt
** Attachment