Email Deliverability Strategy Essentials. 15 min read

Deliverability isn't a binary delivered-or-bounced metric. It encompasses inbox placement (did the email land in the inbox or spam folder?), rendering (did it display correctly?), and engagement (did the recipient interact with it?). The metric that matters most is inbox placement rate — the percentage of emails that reach the primary inbox rather than the spam folder, promotions tab, or junk folder.

Most ESPs report delivery rate (emails accepted by the receiving server). This number is almost always above 95% and tells you very little. An email can be 'delivered' to the spam folder. Inbox placement rate requires specialized monitoring tools like Seed Lists or Google Postmaster Tools and gives you the real picture.

Email authentication is the non-negotiable foundation of deliverability. Three protocols work together:

SPF (Sender Policy Framework) publishes a DNS record listing authorized sending IPs for your domain. Keep your SPF record under the 10-DNS-lookup limit. Use include mechanisms for ESPs and ip4/ip6 for your own infrastructure. End with -all for hard fail.

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to each email. Configure custom DKIM with your own domain (not the ESP's default domain) and use 2048-bit keys. Rotate keys annually.

DMARC (Domain-based Message Authentication, Reporting & Conformance) ties SPF and DKIM together with a policy. Start at p=none for monitoring, move to p=quarantine at 10% then 50% then 100%, and finally p=reject. Process aggregate reports weekly to identify authentication gaps.

Since February 2024, Google and Yahoo require all three for bulk senders. Non-compliance means your emails go to spam or get rejected.

Your list is an asset that depreciates over time. Email addresses go stale as people change jobs, abandon accounts, or simply lose interest. Without active maintenance, list quality degrades at a rate of 20 to 30% per year.

Implement these hygiene practices: validate email addresses at the point of collection using real-time verification APIs. Use double opt-in for new subscribers — it reduces list size by 15 to 20% but dramatically improves engagement quality. Run periodic re-verification of your existing list to catch addresses that have become invalid.

Sunset policies are essential. Subscribers who haven't opened or clicked in 90 days should enter a re-engagement sequence. Those who don't respond to re-engagement within 30 days should be suppressed. This feels counterintuitive — removing subscribers seems like it shrinks your audience. In practice, it improves your engagement metrics, which improves your reputation, which improves inbox placement for your remaining subscribers. The effective reach of a clean 50,000-person list is higher than a dirty 200,000-person list.

Your sender reputation is a score that mailbox providers assign to your domain and sending IPs based on your sending behavior. It determines whether your emails reach the inbox or the spam folder.

Reputation is built on several signals: complaint rate (keep below 0.1%), bounce rate (keep below 2%), spam trap hits (should be zero — if you're hitting spam traps, your list hygiene is failing), engagement metrics (higher open and click rates improve reputation), and sending consistency (steady, predictable volume is better than erratic spikes).

Monitor reputation through Google Postmaster Tools (for Gmail), Microsoft SNDS (for Outlook/Hotmail), and your ESP's deliverability dashboard. Check weekly at minimum, daily during high-volume sending periods.

If reputation drops, the recovery playbook is: immediately stop sending to unengaged subscribers, audit recent changes to your sending (new list sources, content changes, volume spikes), resolve any authentication issues, and gradually rebuild by sending only to your most engaged segments. Recovery typically takes 2 to 4 weeks of disciplined sending.

Separate your sending infrastructure by mail type. Transactional emails (order confirmations, password resets) and marketing emails should use different subdomains and ideally different IPs. This prevents marketing reputation fluctuations from affecting your critical transactional deliverability.

For brands sending more than 100,000 emails per month, dedicated IPs are worth the investment. They give you full control over your sending reputation — no other sender can contaminate it. But dedicated IPs require proper warming: start with 5,000 to 10,000 emails per day to your most engaged subscribers, increase by 20 to 30% daily, and reach full volume over 4 to 6 weeks.

Configure feedback loops with major mailbox providers. When a recipient marks your email as spam, the provider notifies you, and you should immediately suppress that address. Not processing feedback loops means you keep sending to people who've actively told their mailbox provider they don't want your email.