Host your own mail server, it takes less than a day of work per year to keep things running smoothly and you always know where your data is hosted. Use a smart server for outgoing mail - your IAP most likely mandates this by blocking port 25 outgoing - and configure your MTA correctly to make sure your mail does not get bounced by Google or Microsoft (the most likely culprits to do so in my experience). Use Dovecot as MDA and access your mail from whatever IMAP client you happen to like - Claws mail, Thunderbird, K9, etc. Use Sieve [1] to filter your mail into separate folders, including a spam folder for messages marked as such by SpamAssassin which is used by the MTA to check for such.

What I use:

- MTA: Exim, greylistd + SpamAssassin for spam filtering

- MDA: Dovecot with dovecot-sieve for filtering

- MUA on Linux: mutt, claws-mail

- MUA on Android: K9

- MUA on web: Rainloop as a Nextcloud app, Roundcube standalone

I've been doing this for more than 25 years and never had any significant problems. I get far less spam in my inbox than I see in the Gmail account I registered back when that was a new thing and which I only use for testing purposes. If I am to believe the naysayers on this forum and elsewhere it is impossible to host your own mail but my experience shows they are simply wrong.

Just get a SBC, install a mail stack (MTA + MDA, Sieve, SpamAssassin, some form of greylisting if you want to use that) on it, hook it up to your residential connection, get a domain name and start experimenting.

[1] https://en.wikipedia.org/wiki/Sieve_(mail_filtering_language...