It's almost certainly because your customers are reporting your emails as spam by moving it into the junk folder which is training their systems.

Once enough of your customers do this to cross a certain threshold, you are identified as an undesirable sender and QED.

▲

dijit 2 hours ago | parent | next [-]

It happens at scale.

There's like a middle scale where you're not big enough that Microsoft will go out of their way to whitelist you, but you're big enough that your "send to junk" rate is just high in terms of absolute numbers.

It's certainly not a ratio, it must be based on absolute numbers because I've seen it too many times across too many companies, and the only ones that get away with it are extremely low volume.

Once you have 1,000,000 mails, even a 0.1% mark as spam rate is 1,000 emails. - and some people treat mark as spam as their delete button, certainly more than 0.1% of people. Don't ask me why.

EDIT: on inspection; it's worth noting the mechanism is even more insidious than "people mark you as spam". Microsoft also weighs delete-without-opening as a negative signal. So if you're sending transactional mail (receipts, shipping notifications, invoices) and your users get exactly what they wanted, feel satisfied, and bin it without opening. You've just taken a reputation hit for doing your job correctly. The senders most at risk aren't the ones sending rubbish.

EDIT2; theres a reply to me that I can’t reply to because its [dead]; though the point is valid so I vouched. To them I say: I agree. But you probably want your receipt, and thats the example I gave (for a reason).

	▲	LorenPechtel an hour ago \| parent \| next [-]
		Delete without opening shouldn't be treated as negative. I generally keep the stuff on your list, but I almost never open the it's-your-turn e-mails--the title contains everything I need to know. And, likewise, Meetup notifications--I dump most of them unread as the title is enough to tell me I'm not interested in that event.
	▲	andrewmcwatters an hour ago \| parent \| prev [-]
		Because everyone and their mother sends spam. It doesn't take a genius to figure out why. No, I don't want emails about the new product you're releasing. No I don't want your newsletter. I have to actively fight to keep my inbox empty, and free of crap. And while I'm ranting, notifications I actually want on my phone are co-opted by advertisements, which Apple and Google should actively prevent, but they won't because they use push notifications to commingle advertising to you with important, sometimes time-sensitive notifications. Everyone thinks they have something worth sharing. Over three nines of the time, people don't. I will happily be apart of the 0.1% who sends your crap straight to the spam filter for Gmail to train. It's spam. It's almost all spam. Even the transactional stuff for logging in, I don't want. Just use an email, password, and TOTP. Stop sending me emails. Stop it.

▲

adrian_b 2 hours ago | parent | prev | next [-]

I do not think that is true.

Once when this happened to me a couple of years ago, it was the opposite.

My e-mails were put by default by Microsoft as spam into the junk folder, without the customer knowing anything about this.

After I succeeded to notify him about this, he searched there the e-mails and marked them as "not spam", and then he received my following e-mails.

So initially the customer did nothing and was not aware that some of the e-mails sent to him are classified as spam, and he had to do active efforts to override this default action by Microsoft.

There was absolutely nothing suspicious about the e-mail messages classified as spam in their content, their only fault was not coming from one of the few major e-mail providers.

▲

bluecalm an hour ago | parent | prev [-]

Almost certainly not. Microsoft was the only email provider we had problems with a few years back. We only sent emails to people who paid us several hundred USD to send that email. We didn't sent anything else - no follow ups, marketing, announcements, nothing.