Mails not sended

Hello!

I have again the problem that RT from time to time has problems to send mails.
But in the logs I have a new error message

Scrip Prepare 158 died. - panic: attempt to copy freed scalar 7f89fe68dc08 to 7f8a641ca550 at /usr/local/share/perl/5.18.2/Devel/StackTrace.pm line 59

any ideas?

METADATA:
rt 4.2.11
Ubuntu 14.04
apache/mod_perl2

Sven Sternberger
System Engineer
Tel.: 040/8998-4397
DESY IT