Hello,
Please make sure the “FROM” address on your server is valid, and also, it would be better if you use SMTP to send out the email, SMTP is the most authentic way for the delivery of the emails. PR uses WP_MAIL function to send out the email, so any plugin that overrides WP_MAIL and use SMTP to send out email will work for PR as well.
Please feel free to let us know if you have any questions.
Thanks