I tried to self host my email but I immediately ran into the issue that basically every ISP and VPS host available to me block outgoing connections on the SMTP

I tried to self host my email but I immediately ran into the issue that basically every ISP and VPS host available to me block outgoing connections on the SMTP ports. This is a fairly new development in the last few years and is done mainly so that users can't cause their providers to end up on a blacklist. For some time it was possible to just send a special request to the provider asking them to unblock the port, but this is becoming less common, for often they simply deny the request. Users who have been hosting their own email for many years have often been grandfathered in so they might not even be aware of this.