The Complete Email Deliverability Guide

None of your email marketing matters if emails go to spam. A 40% open rate on a 70% inbox placement rate means 30% of your list never had a chance to see your email.

Deliverability is not a set-it-and-forget-it thing. It requires ongoing monitoring. Sender reputation changes based on your sending patterns, list hygiene, and engagement metrics.

SPF tells inbox providers which servers are allowed to send email from your domain. DKIM adds a cryptographic signature proving the email was not altered in transit. DMARC tells providers what to do when these checks fail.

All three are mandatory. Without them, your emails are treated as suspicious by default. Most deliverability problems we see start with misconfigured DNS records.

SPF has a 10-lookup limit. If you use multiple sending services (marketing ESP, transactional service, helpdesk), each counts toward that limit. Exceeding it causes a silent failure.

DKIM keys should be rotated annually. Set a calendar reminder. Outdated keys are a security risk and some providers downgrade trust over time.

Start DMARC in monitoring mode (p=none). Review reports for 2-4 weeks to identify all legitimate sending services. Then move to quarantine, then reject.

New sending IPs and domains have no reputation. Inbox providers treat them as unknown senders. Sending high volume immediately triggers spam filters.

A warm-up schedule starts with small volumes to your most engaged subscribers. Day 1: 200-500 sends. Increase by 50-100% daily. Most warm-ups take 2-4 weeks to reach full volume.

During warm-up, monitor bounce rates, spam complaints, and inbox placement daily. If bounce rates exceed 3% or spam complaints exceed 0.1% on any day, pause and investigate.

Dedicated IPs are recommended for senders doing 100K+ emails per month. Below that, shared IPs from reputable ESPs are fine. The risk with shared IPs is that another sender's bad behavior affects your reputation.

A clean list is the single biggest factor in deliverability after DNS authentication.

Remove hard bounces immediately. Most ESPs do this automatically. If yours does not, switch ESPs.

Suppress contacts who have not engaged (clicked) in 90 days. Move them to a re-engagement flow, and if they do not re-engage in 14 days, suppress them permanently.

Run your list through an email verification service quarterly. This catches addresses that have become spam traps (recycled addresses that providers use to identify bad senders).

Never buy, rent, or scrape email lists. The short-term growth is not worth the deliverability damage. We have seen brands lose months of progress from a single bad list import.

Check Spamhaus, SURBL, Barracuda, and URIBL weekly. These are the major blacklists. Getting listed on any of them drops inbox placement dramatically.

If you get blacklisted: stop sending immediately, identify the cause, clean your list, submit a delisting request with documentation of what you fixed, and warm up again.

Use seed list testing before major sends. Services like GlockApps and Inbox Monster show you where your email lands (inbox, spam, promotions) across Gmail, Outlook, Yahoo, and Apple Mail.

Track inbox placement as a weekly KPI alongside revenue and list growth. If it drops below 95%, investigate immediately.