Might just be that the domain needs warming. Is the domain brand new? Also, check if the IP is the same when you send from Supabase vs. your node script. In gmail, you can click «Show original» or similar.
Are you the guy advertising for BackupDrill again?
So this was just an ad .\_.
I agree, but my SMTP relay is just an add-on to my API to make it work with Supabase.
Check out https://eusend.dev
I also want to use it for other stuff, not just Supabase. Supabase only supports SMTP in the web interface.
https://eusend.dev looks promising.