North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Misguided SPAM Filtering techniques
On 21/10/2007, at 9:12 AM, Owen DeLong wrote:
Blocking 25/TCP is acceptable, blocking 587/TCP is not - it is designed for mail submission to an MSA, so serves little use for spam, save when a spammer has detected an open mail relay listening on 587/TCP, or someone has (mis)configured port 587 to allow submission to locally hosted domains from remote hosts without authentication. I'd be /very/ surprised if the networks in question received sufficient complaints from (clueless) mail admins, who were being spammed via one of these techniques. http://www.ietf.org/rfc/rfc2476.txt I find blocking this sort of thing pretty despicable and surprising. You should test that port 587 actually is blocked (and not appear that way as a function of some other anomaly), and then provide their technical people with a swift kick to the backside. In the short term, your alternative may be to use 465/TCP. (smtp+ssl) Blocking 25/TCP prevents people running their own mail MSAs on their connection, and that's fine, many T&C's don't allow that. Blocking 587/TCP prevents people using someone elses mail service. I view the latter as no different to preventing you viewing someone elses website. -- Nathan Ward
|