Sender email

You should have a form field for default sender address near the test email. If the admin’s address is from a different domain, the emails get caught in spam for failing to validate because the spf and dkim etc is set for the domain the wordpress is hosted on.

I had to hack the plugin source to put an email from my domain as a sender.

Individual newsletters seem to have the capability to have individual senders. If someone forgets to set this correctly from the domain of the site sending the email, the whole newsletter will be flagged as spam. I have never found this necessary. I am also concerned that it may result in abuse if non-admins have authority to create and send out newsletters. For example a disgruntled employee asked to push out a routine update sending out a newsletter that appears to come from his boss… Newsletter should have a default sender. It works well.