Newsletter starting from an HTML page
Yes, when writing a new newsletter, select the option “Import a message from the internet”. Then insert the access link with copy-paste from the address bar of the browser in the corresponding field.
Please note that some differences might occur when importing, depending on the complexity of the imported page.
You also need to avoid all the “exotic” languages (JavaScript, Flash and other CSS) which are not interpreted by the email clients (Outlook, Thunderbird, Gmail, etc.).