My business email ISP provides a BoxTrapper. In there, you can see "trapped" emails awaiting a decision from me. "View any BoxTrapper mail waiting for verification"

Decisions can be:

Whitelist and deliver
Deliver
Blacklist
Ignore

and so on. I can't give you the complete list right now, because I've cleared them all out today.

If I select "Blacklist", they join the BoxTrapper BlackList.

Here is the text at the Blacklist page:

The blacklist is a list of content you do not wish to receive in email. The sender of blacklisted content will also receive a warning message of your choice.

The list should contain one entry per line. Each entry should be formatted as a Perl regular expression.
For example: john@example.com would be john\@example\.com and all addresses at example.com would be .+\@example\.com


Looking at the Black List, I can see how many different domain names (all fictitious) which this lot have used recently:

from pamela\@criticalvieweyeprotection\.com
from susan\@criticalvieweyeprotection\.com
from jennifer\@phoenixrisenmultimedia\.info
from susan\@phoenixrisenmultimedia\.info
from meredith\@dallashollandergallery\.com
from scorecheck\@dallashollandergallery\.com
from pamela\@craftspotonline\.com
from susan\@craftspotonline\.com
from susan\@julissawellsfashions\.com
from pamela\@julissawellsfashions\.com
from susan\@meesoacademy\.com
from jennifer\@meesoacademy\.com

And So On. And on and on and on and on. Every day.........