Maybe this could be achieved with a custom token. The feature request would be slightly different then just a global block list. It may be more versatile to have this ability. For example if you were able to make a token called “global_blocklist” that included the domains you wanted to include you could then insert {{global_blocklist}} into the “Email domains to block” field.
To my knowledge you cannot currently make a list of companies (domains), maybe this ability could help ease the development of the block list. If you could make a company (domain) list the feature of excluding them from forms could work similarely to excluding a contact list from a workflow.
Another option might be to have a field that set a block property at the company level. Essentially you could block all form submission for a company with the ability to overide at the contact level.
We use a custom “competitor” field for companies with a workflow that copies that field to any new contacts created with the same domain. Additionally we have an “active” list of all contacts with the value of “yes” in the competitor field that can be excluded from any workflow. This workaround may be helpful for others who are awaiting the blocklist feature.
Considering this feature was requested over 2.5 years ago it would be nice to see some sort of progress.