How to Completely Block Someone on Tumblrby Andy Walton
Tumblr's social features are a key part of the site's popularity, allowing users to talk to each other and share each other's posts. However, as with any social network, these features could also be used to send bullying or inappropriate content to other site users. You can avoid this scenario using Tumblr's Ignore function, a blacklist of users that you don't want to contact you. Once added to your Ignore list, a user is removed from all your Dashboard notifications and can no longer send you messages.
Sign in to Tumblr and open Tumblr's “Ignore” page (link in Resources) to display the Ignored Users box.
Enter the username of the person that you wish to block into the Ignored Users box.
Click the “Ignore” button to add the user to your Ignore list. Alternatively, if you do not know the person's username you can enter the URL of their main Tumblr blog.
Although ignored users won't see your blog posts on their Dashboard, they can still read any public posts that you make by viewing your main blog page.