Its now failing with this after deleting around 200, but its now stuck:
ActiveRecord::RecordInvalid: Validation failed: Primary email can't be blank
from /var/www/discourse/vendor/bundle/ruby/2.6.0/gems/activerecord-6.0.3/lib/active_record/validations.rb:80:in `raise_validation_error'
I’ve had a search and found one post about checking for blocked emails in Admin > Logs > Screened Emails and nothing is showing but not sure what to do next. Thanks