In an ideal world, what you say would be true. All senders would have a valid address at which they receive replies.
But like insisting that all incoming messages have valid sender accounts, you're preventing your users from receiving some valid messages. To include this in your scoring scheme makes perfect sense. But rejecting ALL such messages is overkill and if I were paying someone for email service and found that they had such a restriction, I would not be too thrilled with them. Don Ireland -----Original Message----- From: [EMAIL PROTECTED] (Bob Proulx) Date: Saturday, Mar 10, 2007 6:16 pm Subject: Re: Tool for validating sender address as spam-fighting technique? To: users@spamassassin.apache.org Sietse van Zanen wrote: Ralf Hildebrandt wrote: > Kelly Jones wrote: > > To fight spam, I want to validate the address (not necessarily in > > real-time) of the a given email sender. Is there a Unix tool that > > does this? > > Postfix has exactly this built in. It's the > "reject_unverified_sender" restriction. > Yes, but you don't always want to reject such mails. NDR's, automated mails etc are often send from empty or non-existent e-mail addresses. Any legitimate email will have a valid sender address. That includes DSNs and automated messages. Within a small network it may be okay to use an invalid sending address locally. But for any mail across a wan the sending address must be able to receive bounces. So yes I do want to always reject mail with invalid sending addresses. The postfix and exim implementations are great. But I also see where this would be very useful to do off-on-the-side of the mta for a corpus of mail. I do spam filtering for a number of mailman hosted mailing lists. For various reasons outside my control this is not done on the front end machine. It would be useful to be able to use verified senders to catagorize mail as it is processed through the pipeline. Having a tool outside of the mta to provide this data would be very useful to me anyway. Bob
