On 10 Apr 2014, at 07:58 , Marcin Szymonik <szymoni...@gmail.com> wrote:
> Hello, > > We run a free accounts mail server (like gmail) and we struggle with the > outgoing spam problem. > Spammers abuse our service by creating accounts and then sending out spam. > > It is very easy and free to create an account and we want it to stay that way > so blocking or removing spammers accounts is not a solition - they can easily > create many new accounts. > They use tens of different IP addresses and send from different locations and > countries so per IP limits really don't work. > Many of their IPs aren't listed on any RBL at all. > I feel it would be hard to filter them by message contents - they avoid > patterns by changing headers (even an encoding), message texts or links if > they add any. > > How can we fight this? Require a valid email address to send a confirmation for account sign up. Restrict new accounts to sending email only to one destination address. Restrict new accounts to a few dozen emails a day and restrict ALL accounts to something like 100 a day maximum unless they request an increase and seem legit (this requires human intervention). The alternative is to have your system blacklisted as a spam source. Keep in mind that many mail admins will have their own blacklists, so even if you don’t get on RBLs or get cleaned up and off RBLs, you may never get off a particular mail-server’s blacklist. > How other free mail service providers block this? Some implement Captchas, but as a user I find these horribly annoying and it often takes me 4 or 5 attempts to ‘solve’ them. I also don’t think they are at all effective as the botnets and spammers have networks of people solving them for them. -- If you could do a sort of relief map of sinfulness, wickedness and all-round immorality, rather like those representations of the gravitational field around a Black Hole, then even in Ankh-Morpork the Shades would be represented by a shaft. In fact the Shades was remarkably like the aforesaid well-known astrological phenomenon: it had a certain strong attraction, no light escaped from it, and it could indeed become a gateway to another world. The next one.
