But when I try and send them an email i reiece the following message
Address not found
Your message wasn't delivered to
support@coinbase.com because the address couldn't be found, or is unable to receive mail.
I think sending them an email directly cause some sort of problem.
I remember there was someone who did the same thing with one of Coinbase's known support email addresses. Though his email has not bounced back, he hasn't received an automated reply that his case was received by Coinbase so there was no case number either. This is a pretty important step as without said confirmation/case ID, I doubt you're in queue.
As mentioned above, they have streamlined support ticket through on-site form and you should use that instead.