Supabase auth emails not arriving on Outlook/Hotmail

Signup confirmations and magic links never reach Outlook, Hotmail or corporate Microsoft inboxes. Other providers receive them fine.

Two real causes:

1. The built-in Supabase email service is rate-limited and shared — fine for testing, not for production delivery.
2. Microsoft filters unauthenticated senders aggressively.

Set up custom SMTP (Resend works well): verify your domain, add the SPF and DKIM records, then point Supabase Auth → SMTP settings at it. Emails start landing, including Microsoft inboxes.

Jul 16, 2026, on a real support case.