Can you recommend a newsletter plugin? This will save me a lot of time since there are several newsletter plugins to test. I prefer the following features.
wordpress user signup form or profile page has "Subscribe to newsletter" checkbox, that can be set to a default value by the admin.
mailing list for newsletter drawn from the wordpress user list. No separate list of newsletter subscribers.
newsletter only sent to users with "Subscribe to newsletter" setting enabled.
The content of the newsletters can be edited by the admin on a editing page online, preferably with an html editor.
after editing the content of the newsletter, have a send button, or move the newsletter to draft status.