This is a question many people ask, and one that has a complicated answer. While it is possible to mail a newsletter without an envelope, there are a few things to keep in mind.
First, make sure the newsletter content is properly formatted for email delivery. Most email programs have a template or format that allows you to easily create and send newsletters.
If your newsletter content does not fit within this format, it may not be delivered effectively.
Second, consider including an email address for people to unsubscribe from your newsletters if they no longer want to receive them. Including an unsubscribe link in the body of your newsletter will help ensure that people who no longer want to receive your content have the opportunity to do so.
Finally, always test your newsletters before you send them out! Although mailing without an envelope can be done successfully, it is always best to be sure that your content will be delivered without issue.