When people receive the newsletter, the sender’s email is the username and email @ my host and not the name of my site and the corresponding email.
I checked in the settings and put all the information in “general settings”.
Moreover, when I preview the newsletter, it shows the correct address as the sender but when the newsletter is sent, the sender’s email is different.
Probably the provider is forcing it to a specific value OR you have an SMTP plugin changing it on outgoing emails. Newsletter always uses the one set inside the main settings or the one set on the single newsletter configuration.