Editing Anti-spam techniques (section)

=== Collateral damage ===

{{See also|Scunthorpe problem}}

Measures to protect against spam can cause collateral damage. This includes:

*The measures may consume resources, both in the server and on the network.

*When a mail server rejects legitimate messages, the sender needs to contact the recipient out of channel.

*When legitimate messages are relegated to a spam folder, the sender is not notified of this. 

*If a recipient periodically checks his spam folder, that will cost him time and if there is a lot of spam it is easy to overlook the few legitimate messages.

* Measures that imposes costs on a third party server may be considered to be abuse and result in deliverability problems.