The default lockrMail setting is that initial emails from new Senders are allowed through to your Primary Destination email address until you decide to Block or set up a Filter for that Sender. If you would like to reverse this setting and block emails from new Senders by default, you can do so by toggling on AutoBlock. You will find this under Settings. Note that by default, we will still allow delivery of account verification and password reset emails from all Senders, even when you have AutoBlock enabled. You can disable that setting on an overall basis also from the Settings section of your account, or on an individual domain basis under Domains