cancel
Showing results for 
Search instead for 
Did you mean: 

Messages from the Event Horizon

Mark_Dowd
Grafter
Posts: 102
Registered: 08-08-2007

Messages from the Event Horizon

Hi.

I'm sure I read somewhere that spammers consider email addresses that do not respond in the negative to be valid (unfortumately I can't remember where I read this, despite searching until the wee hours).

Does/can the black hole address send a "not found here" SMTP response, prior to trashing the mail, or will this merely end up in another innocent's inbox?

Regards :-)
2 REPLIES
csogilvie
Grafter
Posts: 5,852
Registered: 04-04-2007

Messages from the Event Horizon

Its highly likely that it will end up in another inocents mailboxes as with Virus emails etc. the From Address is invalid - this is also one reason you should never use the "Bounce" option in programs such as MailWasher, you can just be adding to the problem
N/A

Messages from the Event Horizon

This links into another idea posted here, to allow users to define valid mail addresses for their subdomain. Anything outside that would be dumped.

The only half-good way to do this is at SMTP connection time. If you try to mail fakeuser@tranchant.plus.com, my server will reject your connection before you send any headers:

Quote
220 tranchant.plus.com ESMTP Sendmail 8.12.11/8.12.11; Wed, 14 Apr 2004 13:52:10 +0100
EHLO localhost
250 tranchant.plus.com Hello localhost [127.0.0.1], pleased to meet you
MAIL FROM:<alice@example.com>
250 2.1.0 <alice@example.com>... Sender ok
RCPT TO:<fakeuser@tranchant.plus.com>
550 5.1.1 <fakeuser@tranchant.plus.com>... No such user here


...and that's game over. No wasted bandwidth sending the message prior to rejection.

This will still result in an unnecessary bounce message if the spammer used a valid but spoofed MAIL address and sent it via a relay. Other filters I use will reduce the likelihood of such a combination getting this far, but this sort of rejection is a good thing to do for valid mail, such as typos in the address.