by Kate Rhodes.
Thank you, but I don't know if this helps. I don't usually get messages back from the servers who block the email. The confirmation email just doesn't get deliver to the recipient at all, and their account remains unconfirmed. The user usually contacts me to say they didn't receive the email so I go into the site and manually confirm them.
I do get messages when an email can't be delivered because of an invalid email address, but it doesn't seem like I ever get the ones that are blocked.
And if I did, I wouldn't know the first place to look to remedy the issue even if I saw the headers and the message.