My mail server is better at not losing mail than Plusnet, better at not hiding things than Google, has effectively unlimited storage and is faster than my internet connection. Given that it's a toss up between hosting it locally or paying for an equivalent service elsewhere, I consider it the path of least resistance. Of course, there isn't any Windows involved, which helps.
I had a problem with BT's mail server treating all my outbound mail as spam a couple of days ago. So I resurrected an old mail server and routed all my mail through that, only to find that BT broadband won't allow subscribers to use their own mail server.
It bounced all my outbound mail with a lovely message that "It is the policy of BT Retail that unauthenticated email sent from this IP address should be sent out only via the designated outbound mail server allocated to BT Retail customers. Please consult the following URL for details on how to configure your email client appropriately."
That was a great help. Even more helpful was BT's online support, who advised that they would need to excalate the issue to their second-line support in India, who would be happy to get back to me once the lockdown there was over.
Happily, as these things do, the problem resolved itself the next day, though it left me considering carefully who my next ISP should be ...