I'd be interested in understanding the privacy implications of AWS. Are there TOS terms that give Amazon the right to look into your instance and analyse your data? At a minimal they certainly see DNS querys.
For true email self-hosting, consider this guide:
And run your own authoritative DNS server as well...
This is clearly in between where you are hosting the domain and services, albeit the compute is leased.
The phrase "hosting the domain" is also subject to the same conclusion. Registering a domain for use by a 3rd party service provider is not the same as "hosting" the DNS. To actually host DNS requires running an authoritative DNS server. Self-hosting DNS would imply running this service yourself, not using a 3rd party DNS service provider.
I hear you, but, again, it's a spectrum and you don't need your own DC or colocation or homelab to "self host".