I am unable to send emails and am getting the error "Outgoing blocked: Unusual activity detected. To unblock your account, please and submit a request.  Learn more.". 

I am unsure as to why this is happening since all my activity is legitimate, mainly confirmation emails for my site's newsletter and account signups.

I have already submitted a request to get the account unblocked but have not received a response yet. This issue is quite important as in the meantime, no one will be able to create an account or signup for the newsletter.