Deliverability is whether your emails reach the inbox. It is decided far more by who you send to and how they react than by clever wording. Work through this checklist in order.
1. Authenticate your domain
- SPF tells receivers which servers may send for your domain.
- DKIM signs messages so tampering can be detected.
- DMARC tells receivers what to do when SPF or DKIM fails, and gives you reports.
Use a dedicated sending domain or subdomain on your brand, not a shared default, so your reputation is your own.
2. Meet the Gmail and Yahoo bulk-sender rules
Large mailbox providers set requirements for senders who email in volume: authenticated mail, a one-click unsubscribe in marketing messages, prompt handling of unsubscribe requests and spam complaint rates kept low. Review each provider's current sender guidelines, because the thresholds are enforced and updated over time.
3. Send to people who want your email
- Use clear consent at sign-up. Never buy or rent lists.
- Send most campaigns to engaged segments (for example, people who opened or clicked recently, or who purchased).
- Run a sunset policy: reduce or stop sending to contacts who have not engaged for a long period, with a final "still interested?" attempt first.
4. Keep the list clean
Suppress hard bounces and invalid addresses automatically, remove obvious typos and role accounts that never engage, and watch for sudden spikes in sign-ups from bots. Cleaning also lowers your platform bill.
5. Warm up new domains and big sends gradually
A new domain, or a long-dormant one, has no reputation. Start with your most engaged contacts, increase volume steadily over a few weeks, and avoid sudden jumps from a few hundred to your whole list.
6. Make content match expectations
- Subject lines that reflect the email, not bait.
- A recognizable "from" name and address.
- A sensible text-to-image balance and working links.
- A visible unsubscribe link. An easy exit is better than a spam complaint.
7. Monitor, do not guess
- Check Google Postmaster Tools for domain reputation and spam rate.
- Track bounce, unsubscribe and complaint rates by campaign.
- Judge success by clicks, conversions and revenue per recipient. Open rates are distorted by privacy features; see why open rate is a weak metric.
When emails land in spam anyway
Stop sending to cold segments, confirm authentication still passes, check for a recent list import or a spike in complaints, and resume with your most engaged contacts. Include deliverability in a regular account audit, and make sure your initial setup covered the foundations.
Quick answers
How can I improve email deliverability?
Authenticate your domain with SPF, DKIM and DMARC, send to engaged subscribers, remove invalid and long-inactive addresses, make unsubscribing easy and keep spam complaints very low.
Do spam trigger words still matter?
Far less than people think. Inbox providers weigh authentication, sender reputation, engagement and complaints much more heavily than individual words, though misleading subject lines still hurt trust.
What spam complaint rate is acceptable?
Google advises keeping the spam rate reported in Postmaster Tools under 0.10% and never reaching 0.30%. Staying well below those thresholds protects your inbox placement.
Tehseen Arbab
Retention and lifecycle marketer for DTC supplement and coffee brands. I led retention for a supplement brand whose monthly run-rate grew from about $500K to $700K, and I work in Klaviyo, Skio, Recharge, Meta Ads and Shopify.