Some actual data presented anecdotally

Posted Jul 11, 2011 22:26 UTC (Mon) by lindahl (guest, #15266)
In reply to: Some actual data presented anecdotally by anselm
Parent article: A decline in email spam?

There is a lot of spam designed to look like bounces. It is difficult for the average user to figure out how to ignore them without ignoring real bounces.

Some actual data presented anecdotally

Posted Jul 11, 2011 22:39 UTC (Mon) by anselm (subscriber, #2796) [Link] (5 responses)

Which is why you don't bounce spam. What you want to do is do your filtering during the SMTP dialog, so you don't even need to accept spam (and bounce it later, file it into the recipient's spam folder, or throw it away). You reject apparent spam before your MTA has accepted responsibility for it, and if there is a false positive, the sender gets a nice SMTP error message, from their own MTA, saying their message couldn't be delivered.

(People who won't look at error messages from their own MTA are beyond help.)

Some actual data presented anecdotally

Posted Jul 11, 2011 22:46 UTC (Mon) by lindahl (guest, #15266) [Link] (4 responses)

I get a lot of fake bounces that look like they come from my own MTA.

Some actual data presented anecdotally

Posted Jul 12, 2011 6:56 UTC (Tue) by anselm (subscriber, #2796) [Link]

So what alternative do you suggest?

Here in Germany, if you're handling mail on behalf of other people it is in many cases illegal to just throw stuff away that looks like spam. So you need to either shove suspicious mail into a »spam« folder which the recipients usually look at only sporadically or not at all , or not accept it at all in the first place, by sending error codes during the SMTP dialogue. This applies not only if you are an ISP, but also to many companies, universities, etc.

People will need to figure out how to read their MTAs' error messages. Otherwise, how are they going to deal with mistyped addresses, full recipient mailboxes, etc. all of which can prevent mail from being delivered even in the absence of spam filtering and backscatter. Also, I personally have been a mail admin for 20 years or so, and I have never to my recollection seen a convincing fake error message from my own MTA.

Some actual data presented anecdotally

Posted Jul 12, 2011 14:04 UTC (Tue) by nye (subscriber, #51576) [Link] (2 responses)

>I get a lot of fake bounces that look like they come from my own MTA

Presumably though if you send a message, and shortly afterwards the same message comes back to you with a note saying that it couldn't be delivered to the address you specified, it's not too hard to differentiate that from fake bounces to messages you clearly never sent.

Anyway in practice people obviously do notice bounces, as they generally manage to do just fine in cases where they've typed the address in wrong, for example.

Some actual data presented anecdotally

Posted Jul 12, 2011 23:09 UTC (Tue) by dmarti (subscriber, #11625) [Link] (1 responses)

This is a good use case for SPF. If your mail server has an SPF record, you can reliably filter out real bounces from forgeries. (I read all my bounces, and would much rather have you bounce my mail than stick it in a spam folder.)

Some actual data presented anecdotally

Posted Jul 13, 2011 0:04 UTC (Wed) by mjg59 (subscriber, #23239) [Link]

You can do that without SPF - BATV solves this problem without breaking things like forwarding.