1) You can delete emails from your email address anytime. It will not have any effect in messages.
If you use POP3 then it will automatically be deleted from email address.
You can use gmail/yahoo if you use POP3. goole for respective pop3 setup details.
2) Email address should not be sent between one another. Sender email should always be the “From Email” setup in this plugin or SMTP plugin if you are using. Please recheck and let me know.