For years I had my custom domain serviced by gmail in the background, so don't assume they're not using gmail.
These days I run OpenSMTPD ( https://www.opensmtpd.org/ ) on a server out of my house because I want to minimize my cloud footprint, and OpenSMTPD is orders of magnitude easier to configure than other mail software, and was designed from the ground up to be maximally secure. I've also got it locked to require STARTSSL, which is not recommended but works for the mail I get.
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For years I had my custom domain serviced by gmail in the background, so don't assume they're not using gmail.
These days I run OpenSMTPD ( https://www.opensmtpd.org/ ) on a server out of my house because I want to minimize my cloud footprint, and OpenSMTPD is orders of magnitude easier to configure than other mail software, and was designed from the ground up to be maximally secure. I've also got it locked to require STARTSSL, which is not recommended but works for the mail I get.