[Mimedefang] Powerful anti-spam rule :-)

[Stephane Lentz]

On Sun, Nov 10, 2002 at 08:21:18AM -0500, David F. Skoll wrote:
> ...
> Which does not work.
> 
> > "Verify" a sender address by connecting to the sender's MX server and trying
> > to send a mail. check if the rcpt to: statement with the sender address is
> > accepted. stop the session before the "data" command to avoid actually
> > sending a mail.
> 
> This does not work, because Yahoo returns "250 recipient ok" no matter
> what address you put, as long as it ends in "@yahoo.com".  Try it.
> Yahoo does this to avoid dictionary attacks by spammers on Yahoo
> customers. :-)
> 
=> This will also not work with big companies which have a 2-level
SMTP service :
Internet mail-gateway --- Intranet mail-relay
			  (managing @company.com)

The Internet mail-gateway usually does only relayingi/antispam and 
does not manage @company.com addresses (and therefore only return
"250 recipient ok" too).

Regards, 

SL/
---
Stephane Lentz / Alcanet International - Internet Services