Ok I just received the support answer from Braintoss 
Hi Thomas ,
this is a bad email addess and can not be used:
post+39821f42479a0e5fd35c72b36c5da2acb8348e6b02c8d9c8d4b241a627e62e is an invalid email address.
Kind regards,
Remco
The Support Team
What a great support answer 
Is there a way to change the “Checkvist list E-mail address” to be more “conventional” in order to have it to work with Braintoss ?
Or do you know an alternative to Braintoss ? It seems like the company developing it isn’t doing it as a main buisness. I don’t have the feeling I could rely on it…