Auth Emails Failing / Supabase Auth Help

I’m using Supabase for Auth (with Resend). All auth emails deliver perfectly to my test domains and 10/10 score on mail-tester and other "deliverability" checkers, but my emails sent to gmail and hotmail go to spam or don’t arrive at all. I'm looking to add other options as last resort.

I’m using best practices for email content with no flags on spam checkers.

1 - What could I be missing to have a 10/10 spam approval, but for some gmails and hotmail to be spammed or blocked?
2 - If I switch on other Auth methods, does it give the user the option between email vs facebook etc?
3 - I’m running a UK brand, and Twilo SMS OTP seems pricey for UK customers. Are there any better alternatives price wise?
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