I agree on the technical part, but: A problem is that you can do everything technically right, and sitll land in spam, because some big players don't play by t

I agree on the technical part, but: A problem is that you can do everything technically right, and sitll land in spam, because some big players don't play by the usual rules. For example, Microsoft apparently has an allowlist for IPv4 -- or equivalenty, blocks all IPv4 by default, until you manually de-list them at sender.office.com. At least I haven't found an IP yet for which I didn't have to do that (self-hosting email for 15 years). (Imagine every provider did it like MS; you'd be sitting there and filling out web forms with 1000s of providers.) So you have a technically perfect setup and MS stil rejects you. -- That said, using some provider to send emails for you doesn't solve deliverability either. There, many customers share the same sender IP. If one of them sends marketing/spam, the entire IP gets bad reputation. In such cases, providers recommend to upgrade to "bring your own IP", which then needs to "gather reputation" [0]. Great, might as well have self-hosted in the first place, as repuation is the only thing I bought the service for. [0]: Example: https://www.mailgun.com/blog/deliverability/dedicated-shared-ips-which-one-should-you-use/#chapter-4 https://www.mailgun.com/blog/deliverability/dedicated-shared... -- Especially entertaining is "Use a shared IP if: Your shared IP partners have built a good reputation." As if you had any control over that.