kmail & gpg

Hi all! I have a strange issue with kmail and gpg (TDE 14.0.4, devuan jessie) : When I open kmail and click on an encrypted mail, pinentry-gtk-2 asks for the gpg password once. When I click on any other encrypted mail, it simply opens that mail decrypted - just as i like it. gpg-agent ist running, kpgp is running. On a second computer and different user account when I click on an encrypted mail I get asked for the gpg password every time (which is quite naging with ~ 100 encrypted mails per day). gpg-agent is not running, kpgp is running. Starting gpg-agent by hand does not change this behaviour. So, where should I start to look? Is it correct to assume that kmail starts kgpg which starts gpg-agent? how can I get debug output? Nik -- Please do not email me anything that you are not comfortable also sharing with the NSA.