There is a Block List button at the top right corner of your Connect page. This list allows you to list emails or domains of certain buyers that you do not want Connect to be reaching out to at all. This will apply to all Connect modes (Auto/Manual/ReConnect).
Blocking multiple emails in bulk
If you have a large list of emails that you would like to have blocked on Connect, you will need to separate each email by a comma. An easy way to do this is through excel. Copy and paste your list of emails onto the excel like so:
From here, use the following formula and paste it into your B cell: =A1&","
Select the cell B1, drag the Fill Handle down to the range you need. You will see commas are added at the end of the text in each cell in the help column.
You can then copy and paste your new list of emails with commas included into the Connect block list bar.