I know the answer to this question:
How many addresses can the safe and blocked lists hold?
Approximately 2000 total. This is because the total size of all lists combined cannot exceed 512K. Once the 512K limit is reached, Outlook alerts you and additional addresses aren’t saved until you remove some from the list.
My issue is we have mas amount of email addresses that we would like to block and I have managed to do a registry hack within Exchange to increase the file size limit. However moving onto Office 365, we are not able to hack their system.
The question I have, is there a way of adding a domain to be blocked? for instance @domain200.com. So anything that comes from firstname.lastname@example.org is blocked. Like a wild card, this would reduce the amount of email addresses that we currently have.