Cannot change reply address of my newsletters / in Mailpoet

Hello, I have been using Mailopet for a long time and I thought I knew what I was doing.

I can change the “From” address alright but not the reply-to address.

I tried everything in the Mailpoet settings and in the general wordpress settings but I cannot change the “Reply to:” Header. Which is bad for my newsletter reputation and spam rating.

I appreciate any help!
Thanks
Gregor