Is it possible to send newsletters in ghost hosted on heoku ? if is it how to do that please? and how to edit theme?

i want to set up newsletter for my ghost blog subscriver but it seems to not being possible
how can i do that please

First of all you are gonna need mailgun SMTP credentials. After that you have to configure some settings in the Ghost Admin > Settings.
Check for the settings and try updating mailgun credentials as asked there.
If you face any problem then share with me here with some screenshots of possible.

i already done all of that but i still can’t send newsletter and anybody else can subcribe to the blog except authorised recipients
i want to send to others how can i change the restriction?

for more details:
i add mail to authorised recipents with those mails suscribe and newsletter works but for others it doesn’t work

i want it to work for others email