On 10/04/2014 14:58, Marcin Szymonik 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?
How other free mail service providers block this?
Best regards
--
Marcin Szymonik
szymoni...@gmail.com
I imagine most freemail providers keep a close eye on their abuse
mailboxes, limit the amount of mail that can be sent from any account in
a period of time (and the number of recipients in a single message), and
more than likely run some sort of bayesian (any sort of learning algo
would do) outgoing filter, as well as their incoming ones.
I'd personally stop allowing people to relay through you (unless they
have proven themselves through some arbitrary period of not sending
spam), and by default allow only sending from inside your webmail
application. That's only a place to start, imho.
Nick
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