[BrentOzar]

There used to be a mail provider (EarthLink?) that automatically responded with a message saying I had to click on a link to get my email past their spam filters. I found that infuriating. I can imagine getting one of these automatic responses might cause similar negative reactions - that the person using Inbox Pro is a little bit of a primadonna.

Having said that, I still signed up for the beta. Because I'm a primadonna.

[arn]

This system by itself can be frustrating... as the problem is that they tend to challenge-response everyone.

I would love to see a system that does automatic spam classification (like gmail), but if you get auto-classified as spam, then you get the challenge-response, as a last ditch effort to get through the spam filter.

[jedberg]

That would make it too easy to game the spam system, because now the spammer knows they've been classified as spam, and can keep changing the message until it gets through.

This is why it's generally bad practice to reply to an email telling the sender it is spam.

[arn]

Well, possibly, though spam is a pretty high volume game, and my guess is it's not worth the time for the mass spammers to analyze a few rejects (even if those rejects even do go to their actual address)

It depends on what you prioritize. I prioritize avoiding false-positives, so my spam filter of choice reflects that.

My current spam system (spamstopshere.com) does return bounce/reject messages depending on what filter the email triggers.

[thrownaway2424]

You're wrong. Spammers actively try to monitor their success rates and game the filters.

As for the original idea, backscatter is to be avoided at all costs. Nobody likes bounce messages and so forth for mail they never sent. Much better to reject mail at SMTP time, than generate backscatter to the alleged envelope sender after the fact.

[arn]

So how would you prioritize avoiding false positives without backscatter?

I get a lot of spam, so manually reading a spam folder is not a feasible solution.

[emillon]

Graylisting is more or less this, but instead of a human receiving a challenge, the outbound server receives a "please try again later" (which is enough to stop a lot of spam already).

[krrrh]

Earthlink still does this, at least for some of their customers. It's particularly annoying to be asked to verify your address so that the prima donna on the other side will get their order confirmation or tracking number, and given how many services send automated mail like this from no-reply addresses I'm not even sure how these people shop online. It's a relic from the age before Bayesian spam filters.

[iamrohitbanga]

However I think inbox pro plans to camouflage the link by using an app where the second step will hopefully provide a better user experience. More like an email delivered notification.

[stfu]

This reminds me on TruTwit, in my opinion on of the most spam'iest services on Twitter. But it is some smart disguise.

[samarudge]

You can do this with 'Boxtrapper' on CPanel, or, I believe, with SpamAssassin