- Most of the time, automatically. Some spam control software, on an isp mail server,
will react after a certain amount of mail, in a certain time period, is sent.
This will contact a blacklist server, and submit the sender to blacklisting.
Blacklists are generally based on ips, can be a local pc ip, or a mail sender server ip (smtp).
Once you are on the blacklist, you'll have to contact your isp, or at least your mail service provider,
for a proper removal and instructions.
Incoming mail servers filter content based on blacklist, it isn't rare to see a whole domain
blacklisted by another isp.
For instance, hispeed.ch adresses were blacklisted on aol.com for a long time: aol refused mails
from the hispeed domain for several weeks.
How can I eliminate spam?