Wednesday, September 05, 2007
Some notes from a running graylist server
Man, my email seems eerily quiet now that I'm running the greylist daemon.
I've also identified several problems—nothing related to the code per sé, but to some unintended consequences of competing anti-spam measures (I assume it's an anti-spam measure).
On at least two mailing lists I'm on, the sender address (the one given in SMTP) is unique for every message sent. And to make matters worse, one particular mailing list (it's a Yahoo Group) has come from over 50 different IP addresses. What I'm afraid of is the following scenario: a message M, comes from IP I1 with sender email address S1 getting told to try again later, and when it does, coming from IP I2 with sender email address S2 and thus, I never get the message (even if S doesn't change, the IP address might, and that will still causes problems).
To get around that, I've implemented an IP whitelist, but now the trick is identifying all the network blocks to whitelist. So far, I've whitelisted IP addresses from AOL (two
/16 blocks), BellSouth (two
/18 blocks), and Yahoo (a
/18 block and three
/19 blocks), plus some miscellaneous servers (like my server at Casa New Jersey, just in case).
Update on Thursday, September 6th, 2007 at 1:40 am
Yup, the mailing lists are going to be very problematic.