Email Deliverability
Deliverability is the percentage of emails you send that actually reach the inbox (vs spam, promotions, or hard bounce). It's the make-or-break metric beneath every email program.
What it is
Deliverability is determined by authentication (SPF, DKIM, DMARC), sender reputation (IP and domain), engagement signals (opens, replies, low spam complaints), list hygiene (low bounce, low unsubscribe), and content (no spam-trigger words or risky links).
Why it matters
Open rate is meaningless if your email is in the spam folder. A 40% open rate on what reached the inbox can mask 60% of sends never landing. Deliverability collapses can happen overnight and take weeks to recover from.
How to protect deliverability
- Authenticate every sending domain with SPF, DKIM, and DMARC (DMARC enforcement is now table stakes for Gmail and Yahoo)
- Warm up new domains/IPs gradually (start at 50/day, double weekly)
- Use a separate subdomain for marketing vs transactional sends
- Suppress hard bounces immediately, soft bounces after 3 attempts
- Run a sunset policy: remove 6+ month unengaged subscribers
- Honor unsubscribes within 24 hours (CAN-SPAM and GDPR)
- Monitor postmaster tools (Google Postmaster Tools, Microsoft SNDS)
Frequently asked questions
What's a good bounce rate?
Hard bounces should stay below 2%. Above 5% triggers reputation damage on most ESPs.
Should I use a dedicated IP?
Dedicated IPs are worth it once you're sending 100k+ emails per month consistently. Below that, a shared IP with a reputable ESP usually performs better because you ride on their established reputation.
Why did my deliverability drop without warning?
Common causes: a hard list growth spike (purchased list), a spam-trap hit, a sudden volume change, content change that triggered filters, or a competitor on a shared IP causing reputation damage.
