The company I'm working for provides free web service ( http://www.skymail.fr ).
This kind of service frequently gets abused by spammers. Two they abuse it:
1) they open an account, just to have a valid address in order to bypass basic spam filters. Then, they send their spam through other servers using this address as the sender.
2) they use scripts to send spam through the service, as any regular user would. This is extremely annoying.
For 1) we publish SPF for all domains we send mail from. Now, it's up to people to enable SPF on their mail servers.
For 2) we filter _all_ packets coming from China, Korea, Nigeria and addresses listed in Spews and Spamhaus databases. That's about 13000+ filtered networks. Thanks to OpenBSD packet filter, it's trivial to set up and it doesn't introduce any slowdown.
This is mandatory for webmails (Score:5, Interesting)
This kind of service frequently gets abused by spammers. Two they abuse it
1) they open an account, just to have a valid address in order to bypass basic spam filters. Then, they send their spam through other servers using this address as the sender.
2) they use scripts to send spam through the service, as any regular user would. This is extremely annoying.
For 1) we publish SPF for all domains we send mail from. Now, it's up to people to enable SPF on their mail servers.
For 2) we filter _all_ packets coming from China, Korea, Nigeria and addresses listed in Spews and Spamhaus databases. That's about 13000+ filtered networks. Thanks to OpenBSD packet filter, it's trivial to set up and it doesn't introduce any slowdown.