A: Hi, thank you for asking.
In MailBluster , You can invite other users into your brand as an Admin, or Manager or Viewer.
In your case, if you want your client to send out email campaigns as well, you can add them in your brand as Admin or Manager.

At the moment MailBluster doesn't support RSS feeds, thank you for the suggestions, we will discuss this with our team.
And Yes, it's hosted in our server.
Please feel free to let us know if you have more questions.