Prior to the Cloud migration, the Mark As Spam resolution initiated a backend process to add addresses to the site-wide blocklist. After going to Cloud, this transition no longer adds accounts to the blocklist, allowing these accounts to still submit requests through email. The manual identification and addition of these spam accounts to the blocklist is the only way to prevent these accounts from submitting email (see below).
Adding Blocklist Entry
From your service project, go to Project settings → Email requests
Select More → Manage blocklist
Select + Add email address or domain
Enter the domain name (do not include @), or the specific email address you want to block
Currently, blocklists only support exact domain matching. For example, adding the domain 'example.com' will match 'firstname.lastname@example.org' but not 'email@example.com' or 'firstname.lastname@example.org'.
The blocklist does not currently support wildcards or pattern matching.