It's terrible to spend a lot of effort on this kind of tech just because some business partner has shitty customer support.
If customer was hosting e-mail servers themselves they wouldn't notify any other mail servers?
Isn't that the whole point of what most of us are doing?
World hunger is not a technical problem. You won't solve it with technical means. If you think you can, you have already lost the fight.
Climate change is not a technical problem. You won't solve it with technical means. If you think you can, you have already lost the fight.
And so on, and so forth. Technical means can help solving certain components needed for the overall solution. These are then technical (sub)problems though. For example, how to store more energy in a battery, or how to grow certain crops with less water. But the overall problems are social in nature. People need to understand that world hunger is a distribution problem. That one is easier to solve with certain (technical) tools available, but that won't be enough. People need to understand that we can't use more natural resources than get replenished. Not a technical problem. If only the tools get better, people will find new ways to be wasteful. Etc etc.
We have observed dramatic technical advances in all fields related to food production in the last 3 decades. We've seen at best marginal improvements in world hunger in the same time, and even that only if you're beeing optimistic with your statistics.
It's sad that VERIFY is basically dead due to spam. In the olden days, you might have been able to use finger - but it's also dead for (among other) similar reasons.
The spam cat and mouse game leads to quite silly situations for benign actors.
For some mx's you might be able to designate some ips as trusted, and do real verify for those.
Keep your "overall bounce rate" low, by ALSO sending out extra emails to confirmed email addresses. Like, for every "confirmation" email, also send a "thanks for joining us" email to someone that already confirmed their email.
In the past when I worked on a system that needed to notify via email we always had a way to change delivery process for certain emails, domains, etc for exactly this reason. This is one of those cases where we would “deliver directly” (i.e. send directly to their mail provider).
Here's one discussion: https://stackoverflow.com/questions/371/how-do-you-make-sure...
We were onboarding a large new client to our SAAS product. This process involved creating accounts for all of their employees (tens of thousands) and sending emails with an activation link. (Where they'd be able to set up their password.)
Our system sends these emails in batches, and as soon as the first batch went out we got an alert from our monitoring system that our bounce rate was surging - high enough to risk a sending pause from Amazon SES. We stopped sending and investigated the issue, and it turned out that the email list we were given was a mess - it included all current employees, but also a huge number of former ones. Just under 1/10th of the emails in our first batch were invalid.
We asked the client to give us a better list, but due to internal issues they couldn't get that to us any time soon. Meanwhile they were breathing down our necks to get these emails out ASAP, and they were a large enough client that our management wanted to keep them happy, so we tried out one of these email validation services. Unfortunately, it didn't work. It turns out that this technique doesn't work for all mail servers. It was reporting every email as valid, even ones we knew were invalid since they'd already hard bounced.
(Edit: thinking back - this was several years ago - I think it wasn't saying that they were valid emails, just that it couldn't tell whether they were valid or not - the service was able to detect that the server wasn't rejecting non-existent addresses.)
We ended up unpausing the emails and just hoping for the best. Ended up with something like an 8% bounce rate that eventually fell off our record as our normal sending patterns resumed. Amazon's guidelines say they might cut you off when you hit 10%, so we cut it pretty close.