Test email works, mail list does not.

I’m not sure what your problem could be at the moment, but please check out this knowledgebase article about information that you should provide in a support ticket. You can send this information to hello at sendpress dot com If you are not comfortable posting that information to the public forms. We will take a look at that information and go from there.

https://sendpress.com/support/knowledgebase/what-information-should-i-provide-in-a-support-ticket/

Got your email. We’ll take a look and get back to you. Thanks.

Your email did not list whether email sending ports are open or not. My guess is your webhost is messing with the sending. Could you try sending with Gmail just to test?

Could you post the part from the help tab that looks like this?

Ports:
Port 25: open
Port 465: open
Port 587: open

I’m curious if they are open or closed.

Your email also looks hosted at that server, is that right? Are you sending to yourself or a different domain. Sometimes email servers are not configured to email themselves from themselves, especially from the wordpress side. Could also affect how the headers look.