[throwanem]

Microsoft is infamous for exactly this behavior among folks who self-host their MTAs. At least with Gmail you can usually figure out where the false positive is and try to do something about it via postmaster tools. Once Hotmail blackholes you, though, that's it forever as far as I could ever tell.

This wasn't the only reason why I switched to Fastmail after 17 years of selfhosting, but it was among them.

[arp242]

Used to work a lot with email, and found all email providers to be workable for false positives (not necessarily "great", but workable/acceptable). Except Outlook 365. Even Google/gmail is tons better at handling these types of things, and that's saying a lot.

[TheNewsIsHere]

A lot of large scale email providers are making it more and more difficult to run your own email infrastructure without also owning/controlling the IP range in which your sending servers are issued their IPs.

I understand the logic, but most of us don’t have control of the IP allocations in which our email servers sit.

Proofpoint was the one that got me to move to Fastmail. They had filtered the entire IP allocation in which my mail server sat at a major cloud provider. Their stance was I could either use whatever email service that provider had, demonstrate control over the entire IP range (just to de-list one IP), or move my server to another IP that wasn’t filtered.

I understand the logic to an extent, but those of us who have enjoyed running our own email services are sort of left in no-man’s-land.