These seem to be the issue:
isValidSmtpServer: Sent from invalid SMTP server.
Invalid sender: info@gromitunleashed.org.uk! Not adding email!
Clear the "Allowed SMTP servers" setting, it isn't needed in you case.
Create a WordPress user for each email address you want to be able to post and set the "Roles That Can Post" setting appropriately.
Alternatively add each email to "Authorized Addresses"
