post by email is currently disabled

HI
I installed, activated, enabled “post by email” and pressed the button check now. I have given no pin. Here is the message that I get :

Fatal error: Call to a member function getHeaderText() on a non-object in /home/infoadrets/www/wp-content/plugins/post-by-email/class-post-by-email.php on line 558

infoadrets.alwaysdata.net

However, I could receive the messages through thunderbird with the same parameters.

Thank you for helping