I have contacted support about this problem, I am just sharing in case others run into problem. Background: The SMTP Blocked Sender list is an effective method for temporarily canceling a domain or indiviual user's ability to send email on the server. For example, if a particular account is sending an abnormal amount of email, you can add their address to Blocked Senders and they will be unable to send email until you remove them from the Blocked Senders list. Users and/or domains can be left on the list for whatever time you deem appropriate, and can be an effective stop-gap versus actually deleting the user and/or domain from the server. Under Security; Advanced; SMTP Blocked Senders add a user email address to list. Log into webmail as user Create and send an email to someone on another server Expected Results: Email is not sent Actual Results: Email is delivered to external user.