[Evolution] PGP Encryption in Evolution

[Andreas Geppert <geppert ifi uzh ch>]

Hi,
when I try to encrypt (and sign) email messages in evolution, I receive
the following error message:

   Could not create message.
   Because "random usage: poolsize=600 mixed=0 polls=0/0 added=0/0 
           outmix=0 getlvl1=0/0 getlvl2=0/0
   secmem usage: 0/32768 bytes in 0 blocks
   ". you may need to select different email options.

The same message (using the same sender and reciver addresses, same
keys) can be encryped and signed in Thunderbird.

How can I make encryption and signing using PGP work in Evolution?

I am using Evolution 3.12.11 on KDE 4.14.9 on OpenSuse 13.2

Is this the right forum to ask such questions? If not, which would be
the right one? Search engines haven provided meaningful results.

Thanks for any kind of help.

Best regards,
Andreas