[ Date Index ][
Thread Index ]
[ <= Previous by date /
thread ]
[ Next by date /
thread => ]
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Simon Waters wrote:
The messages are just bounced earlier, at the backup MX rather than when they can be delivered to the primary MX.If you reject the message from the spammer typically no email is sent to ANYONE!
Yes... agreed. Don't know what the hell I was on about in that paragraph. - -- Snipped stuff about backup MX attack
Like I said earlier, many people will face the situation where their main ADSL hosted mail server could be off for days. Backup MX ensures you get the email full stop, rather than just getting it a bit quicker.Don't run SMTP servers on boxes which are down that long would be my advice, POP3 has to be good for something.
I now have a machine that is always on in the states on which to run SMTP. The advantages of doing my own SMTP on an ADSL box were huge though over using a POP3 hosting account. Firstly I needed a working SMTP server to develop my dissertation project software. Secondly it turned out much mroe reliable than the hosting account I had then... they were bloody awful with large waits for delivery. I could also run mail services for friends at University who wanted to be able to email large(ish) attachments etc not possible with their University or Hotmail accounts. As non computer scientists (i.e. no UNIX access) the only way for them to get files on and off Uni computers was by email or floppy disk.
Interestingly, I actually want spam at the moment for a dissertation project, I'm not out to stop it dead!Getting listed as a back-up MX for a few domains should do the trick. We saw over a 1/3 of all spam go straight to the back-up MXes when we ran them. At this point you are providing the spammer with a no pain method of dumping spam as quickly as possible, where as most MTA's will use back-off algorithmns on connections that attempt to email large numbers of non-existent addresses, backup MXs don't have this luxury.
Of course there is no way to tell if your spam is representative, unless you collect from representative samples of users. There is at least one spam archive on the net which can do you a few tens of megabytes.
Yup... have done considerable research into this sort of stuff. Have 4 good quality corpora for my work, around about 320mb of spam and ham mail. Actually, my spam doesn't have to representative of spam in general. The filter is designed to be trained to work on an individuals spam, a selection of spam of many users causes over generalisation in the training and lower performance for the individual. http://www.trudgian.net/content/spamkann/ I think I might now go and have a look at constructing an exim router and transport config that will silently drop mails (or perhaps freeze, so I can see them) at the backup mx which fail as 550 unknown user on the primary MX. Should be perfectly do-able. - -- Dave Trudgian - Cornish Dave - ---------------------------- [w] www.trudgian.net [e] dave@xxxxxxxxxxxx [j] trudgiad@xxxxxxxxxxxxxxx -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (GNU/Linux) iD8DBQFAfC6pt+PdOLWW6O4RAhC6AJ48r8v5fJsqivindaxIHm4gZ0mq/gCbBtkm v9B0IwaUhf2uh+5YxyaEojQ= =ivfd -----END PGP SIGNATURE----- -- The Mailing List for the Devon & Cornwall LUG Mail majordomo@xxxxxxxxxxxx with "unsubscribe list" in the message body to unsubscribe.