Deliverability is a deep specialty, but list owners get most of the value from a short list of fundamentals.
Authentication (one-time setup)
- SPF: DNS record listing servers allowed to send as your domain
- DKIM: cryptographic signature proving the mail wasn't altered
- DMARC: policy telling providers what to do when SPF/DKIM fail — start with p=none and monitor
- Your send tool's docs have the exact records; the whole setup is an afternoon
The budgets (ongoing)
- Hard bounces: stay under 2% per send — validation before sending is how
- Spam complaints: under 0.1% (Gmail enforces ~0.3% as a hard line)
- Engagement: sustained sends to non-openers teach providers you're ignorable — suppress or win back dormants instead
The habits
- Validate before big sends, always
- Warm up new domains gradually — weeks, not days
- Never buy lists (the addresses are rotten AND the recipients never consented — it fails on both physics and ethics)
- Watch Google Postmaster Tools; it's free reputation telemetry
Run this on your own list.