Error in sending newsletter

Some people reported me the same problem. I’d like that you post some debug info about the issue in order to fix it. You can setup WP_DEBUG to true for php errors and look at the javascript console of your browser for script errors, thanks. You can use plugin forum if you like.

I was able to fix the issue by deactivating & reactivating the plugin.

for me is still not work. any suggestion ?

You can try this faq, maybe it could help you:
https://www.eventualo.net/blog/wp-alo-easymail-newsletter-faq/#faq-20