We are using the plugin and it is working so far. We are using mailgun for sending emails. We have sent mail to users as we only have one list with 437 users. We received a mail today from one of the users that she did not received the newsletter. When we checked the user details the newsletter is not gone to that users but she received previous newsletters. What could be the issue. Please help us resolve it.
I check the profile of the user where you show all the newsletters delivered to that users. Also no mail received by mailgun to sent. So I checked in the plugin as well as in mailgun. My mail sending frequency is 1000.