I created a newsletter, did a "test send" and all worked fine. However when I try to really "send" it, I get a page which says: Sorry, your request cannot be accepted.
I have been able to send newsletters before a few months ago. It's possible the plugin was updated in the meantime (it's not used very often)
Any idea what the reason can be?
Wordpress version 4.9.11, Newsletter plugin 5.8.9
Thanks a lot.
Michiel.