Spam classification is a hard problem, but I don't think they've put the false-positive/false-negative tradeoff in the right place, and they really need some safety valves like offering to whitelist an address when you un-mark it as spam.
Apparently forwarding can sometimes invalidate the SPF or DKIM [1] depending on the settings involved.
But there is a white list, if you add the sender to your contact list it is white listed.
It's horribly convoluted but it /is/ possible to do so:
http://webapps.stackexchange.com/questions/69442/how-to-disa...
I've been running it this way for about 18 months now after having a few important emails get gobbled up by their spam filter.
Never because my grocery store isn't a website.
Amazon can't give you a printed receipt because you are not there, physically. So they send you an email instead.
This is not that hard to understand.
(And keep this discussion in mind next time you read a HN story teaching people how cool e-mail marketing is for your startup - what it's cool at is often pissing off your users.)
Also Google took a good approach to that issue - when an e-mail has an unsubscribe link and you try to mark it as spam, you get asked if you'd like to unsubscribe instead. And yes, I sometimes do exactly that.
1) Unsubscribe should be one click, no confirmation. In the case of accidentally unsubscribing, if it's really that valuable, the person will re-subscribe, and I guarantee it's easy to subscribe because that's already optimized, for obvious reasons.
2) GMail shouldn't give you the option to choose; if you mark something as spam, it should silently attempt to unsubscribe in the background, then keep track of which services don't actually support unsubscribe, and mark those as spam. Far too many people are vindictive and lazy and will intentionally mark things as spam either because they don't want to go through the process of unsubscribing, or they forgot they subscribed, or think they've been "wronged" by getting an email they opted in to.
For the record, I too despise the oblivious email marketing stories on HN, eg the "cold emailing" C level execs whose addresses aren't publicly available. Dirty, dirty, dirty.
so... sorry? :)
That said, this is no excuse for Google to mark their transactional emails as spam for people that clearly want to receive them. Google is just being lazy and doing a bad job. Even Yahoo gets that right, Google can do it too.
of the 64 emails I have from them 50 are spam of this nature.
just because i signed up for amazon.com, doesn't mean they get to spam me crap because they've buried a 2pt font unsubscribe feature that may or may not work over the course of a few weeks.
If you signed up, then you opted in. Don't be lazy and mark things you signed up for as spam. I'm not understanding how people get email from Amazon that aren't customers, and how customers can't turn off everything but confirmations, which I know is possible, because I have.
I'm a customer, I consider that opt out. You don't? I signed up for amazon, not their bullshit emails. That you consider the situation opt in shows they have you trained well.