On Fri, February 13, 2015 12:41 pm, Les Mikesell wrote:
On Fri, Feb 13, 2015 at 12:32 PM, Valeri Galtsev galtsev@kicp.uchicago.edu wrote:
I stated pure observation on at least two pairs of primary - backup MX I maintain. Still I made backup MXes with greylisting as well (they are separately hit by same bad spammers scripts, at a rate about 10 times smaller than primary MXes are and absolutely independently).
I think that's unusual - spammers often target the secondaries as a preference on the premise that they are likely to not be as well-configured as the primary. But it has been a while since I ran one so maybe things have changed.
Consider me lucky...
Still, it is good to have the same greylisting on backup MX. And all other blows and whistles.
Greylisting would be kind of hard to do right. You'd have to keep the known-good senders in sync across the receivers. But my bigger worry would be a dictionary-type attack on user names as recipients if you don't have access to the real user list on the secondary.
With standard backup MX based on postix (with rather trivial configuration) you always do have list of legitimate recipients of primary MX on the secondary MX.
Doing greylisting right means you also have to keep the table of already-known senders up to date and that may be very dynamic.
If you are kind person, yes. Sqlgrey is designed to work simultaneously for primary, secondary (and tretary maybe - didn't check) MXes. Yet, even if they are independent, all will work, you are just not being nice to other servers and make them make 3 delivery attempts (the last is successful) instead of two (that is: primary MX - "temporary failure", secondary - "temporary failure", primary after some time - accepted; instead of primary MX - "temporary failure", secondary - accepted which will be in nice configuration common for both MXes greylisting engine and database).
Valeri
++++++++++++++++++++++++++++++++++++++++ Valeri Galtsev Sr System Administrator Department of Astronomy and Astrophysics Kavli Institute for Cosmological Physics University of Chicago Phone: 773-702-4247 ++++++++++++++++++++++++++++++++++++++++