reply-to not working

[jwit]

I am using the WPForms plugin to setup a contact form in Wordpress. In the form settings the reply-to header is set. That was working for more than a year until this week. Maybe a coincidence but it stopped working when I updated to Wordpress 5.0.

In WP Mail Log the reply-to header is there in the outgoing email:

Headers: From: tester Reply-To: tester@gmail.com Content-Type: text/html; charset=utf-8 Attachments: Error:

but when the email is received the header is missing.