Appreciate the straightforward advice here. I think some people have taken it that I have a burning desire to host email for day to day use but seems like you got it.

Am more looking for something I guess you could describe as an “email archive”. Do you think this is the only way to get what I’m looking for? All these old emails, making them searchable / syncable to different devices with someway of like periodically importing new batches to them?

Okay, good to know, I did see some of those mailservers mention alias’ing but hard to know what they do/don’t do.
I think I maybe didn’t do a good job of emphasising in the post but in a sense it’s not actually a mail server I’m looking for. Its more like a place where I can archive and search through my emails historically if that makes sense? Like all emails older than a year that just get “somehow synced” from my mail big provider email to this place

But it seems that if I want to have that library of emails syncable and searchable across devices, I have to put them within a mail server. Theres nothing which is the equivalent of nextcloud / syncthing for emails you know?