You are able to auto-blacklist a customer, so long as you send them at least 1 message. If you respond to one of their emails they have sent, and BCC your specific blacklist email (for your account being blacklist-XXXX@emailparser.feedbackgenius.com) our system will look at the "to" address and add the Amazon marketplace email address you are responding to, into the blacklist. This may be a bit easier than manually adding each entry into the blacklist. However, this works in the same way because it stops any future emails to that buyer altogether, and not just the next email in the sequence.
To locate your specific blacklist email, please go to your "Blacklist" and click the "i" tooltip.
Alternatively, if you have the setting "Auto Blacklist on Negative Feedback" turned on from your Message Settings a customer will automatically be added to your blacklist if they have left negative seller feedback. For more information, click here.