@lauren @tubsta @DianeBruce @bsdtv @mwl
Agree with that point. In NL it is a bit easier - depending in the provider. Some charge a comparable subscription fee for a "business line" that allows 25/tcp and setting a reverse DNS. Not all do though.
Also it does somewhat depend on the definition of self-hosted. Mine is that you really selfhost it, so under your own roof. But to others it can include VPSes too (which I refer to as self managed).
With my own selfhosted mailserver, I have proper deliverability to the big mailers (Gmail but also Microslop consumer) - 1K of mails to them is not an issue.
Your mileage may vary greatly - and even if the upstream allows 25/tcp inbound and outbound it it not a guaranteed win.