Email Deliverability Checklist: 10 Steps to Land in the Inbox

Landing in the inbox is the first step to any successful email campaign. If your emails go to spam, no one reads them. This checklist covers the 10 steps every B2B marketer should follow to maximize deliverability. Run through these before your next send.

1. Authenticate Your Domain with SPF, DKIM, and DMARC

Email authentication proves you own your sending domain. Without it, receivers treat your mail as suspicious. Start with SPF (Sender Policy Framework). Publish an SPF record listing all servers allowed to send email from your domain. Then add DKIM (DomainKeys Identified Mail) to sign your emails with a private key. Finally, set up DMARC (Domain-based Message Authentication, Reporting, and Conformance) to tell receivers what to do with unauthenticated mail. Start with a monitoring policy (p=none), then move to quarantine or reject once you confirm legitimate sends pass.

For a deeper audit, see our Email Deliverability Audit: A Step-by-Step Guide for Marketers.

Common mistake: forgetting to include all third-party senders in SPF. If you use a CRM or marketing platform, add their IPs or domains to your SPF record. Also, ensure DKIM keys are generated per selector and rotated periodically. Check DNS propagation before sending. DMARC reports can be aggregated via tools like Postmark or Dmarcian to spot alignment issues.

2. Check Your Sender Reputation

Your sender reputation is a score ISPs assign based on complaints, bounces, and spam traps. Use tools to check your reputation on major platforms like Gmail, Outlook, and Yahoo. High reputation means high inbox placement. Low reputation means you land in spam or get blocked. Monitor regularly, especially after a campaign.

How to check: use Google Postmaster Tools for Gmail domain reputation, Microsoft SNDS for Outlook. Third-party tools like SendGrid or Mailgun also provide reputation dashboards. If your reputation drops, pause sends to risky segments, validate list hygiene, and review content.

3. Monitor Blacklists

If your IP or domain ends up on a blacklist, your deliverability plummets. Check common blacklists such as Spamhaus, Barracuda, and SORBS. Remove your IP immediately if listed. To avoid blacklisting, never send to unverified addresses and honor unsubscribe requests instantly.

Set up automated alerts using blacklist monitoring services. If you get listed, first identify the cause. Did you send to purchased lists? Are you getting high complaint rates? After fixing, submit a delisting request. Most IPs are removed within hours if the issue is resolved.

4. Clean Your Email List

A clean list keeps your bounce rate low and engagement high. Remove hard bounces and suppress repeated soft bounces. Use double opt-in to confirm subscribers want your emails. Segment your list by engagement level—send more often to active users, less to dormant ones. This improves metrics that ISPs use to judge you.

Practical steps: run a list hygiene script before every campaign. Remove inactive contacts who haven’t opened in 90 days. Consider a sunset policy: after 6 months of no engagement, send a re-engagement email. If no response, remove them. Also, validate email syntax and domain existence on signup to block typos.

5. Warm Up New IPs Gradually

If you switch to a new sending IP, you start with no reputation. ISPs trust new IPs slowly. Begin by sending small volumes to your most engaged subscribers. Increase volume by 10-20% each day over two to four weeks. Don’t blast a cold list from a new IP—that triggers spam filters.

Prepare a warm-up schedule: day 1-3 send to 500 most active. Day 4-6 send to 1000. Day 7-10 send to 2000. Monitor bounce rates daily. If bounces exceed 2%, reduce volume. Keep complaints under 0.1%. Use a dedicated IP for better control.

6. Control Send Frequency and Consistency

Sudden spikes in volume look like spam behavior. Maintain a consistent send schedule. If you send daily, keep it daily. If you send weekly, keep it weekly. Gradually increase volume if needed. Also, avoid sending to stale lists after long breaks—re-engage them first with a reactivation campaign.

How to decide frequency: test different intervals with small segments. Track unsubscribes and complaints. If you need to increase volume, ramp up over several sends. Use a throttling mechanism in your ESP to spread sends over minutes or hours to avoid spikes.

7. Optimize Email Content for Spam Filters

Spam filters scan your content for trigger words, excessive links, and poor code. Keep your text-to-image ratio high. Avoid spammy phrases like “free” or “act now” in subject lines. Use a plain-text alternative. Ensure your HTML is clean—no broken tags or inline scripts. Check your spam score with a tool before sending.

Also check: include a physical mailing address in the footer. Use a recognizable from name and email address. Avoid using multiple exclamation marks or ALL CAPS in subject lines. Test your email with tools like Mail-Tester.com for a spam score. Aim for a score below 3.

8. Test Inbox Placement Before Sending

You can’t know where your email lands unless you test. Use seed-based testing to see if your email reaches inbox, spam, or is blocked. Send tests to different ISPs and email clients. Compare results across campaigns. Adjust your content and authentication settings based on results.

Tools like GlockApps or Litmus provide seed lists. Test after any major change to your domain, IP, or template. Keep a baseline test for each sending domain. If placement drops, check authentication and content for new triggers. Also test from different geographic regions if your audience is global.

9. Track Engagement Metrics

ISPs watch how recipients interact with your emails. High open and click rates signal quality. Low engagement (especially high spam complaints) signals junk. Monitor your open rates, click-through rates, spam complaint rates, and unsubscribe rates. If complaints exceed 0.1%, review your list and content immediately. Also track bounce rate—keep it under 2%.

Segment metrics by domain. For example, Gmail users may behave differently from Outlook users. Use engagement scoring: assign points for opens and clicks, negative points for unsubscribes. Target high-scoring segments for more frequent sends. For low-scoring, reduce frequency or suppress.

10. Set Up Feedback Loops with Major ISPs

Feedback loops let you know when someone marks your email as spam. Register with the major feedback loop programs (Gmail Postmaster Tools, Outlook Smart Network Data Services, Yahoo Complaint Feedback Loop). When you get a complaint, remove that subscriber immediately. Use the data to identify spikes and investigate what triggered them.

How to analyze complaints: group by email campaign, segment, or subject line. Look for patterns—did a particular offer cause complaints? Also check complaint rates by day of week. Use this data to refine targeting and content. For smaller ISPs, monitor bounce reasons for “abuse” notifications.

Follow these 10 steps consistently. Deliverability isn’t a one-time fix—it requires ongoing monitoring and adjustment. For a foundational overview, read our Email Deliverability: A Beginner’s Guide for B2B Marketers.

Frequently asked questions

What is the most important step in an email deliverability checklist?

Email authentication is the foundation. Without SPF, DKIM, and DMARC, your emails are likely to be rejected or filtered as spam. Start there, then build on list hygiene and reputation monitoring.

How often should I check my sender reputation?

Check your sender reputation at least once a week, and always after a large send. Use tools like Google Postmaster or third-party services to track changes and catch issues early.

What bounce rate is acceptable for good deliverability?

A healthy bounce rate is below 2%. If you exceed 5%, your list likely contains invalid addresses. Clean your list regularly and use double opt-in to reduce bounces.

How long does it take to warm up a new IP address?

Typically two to four weeks. Start with low volume to engaged subscribers and increase gradually. Rushing the warm-up can damage your reputation permanently.

Why do my emails land in spam even with authentication?

Authentication is just one factor. Spam filters also consider content, sender reputation, engagement, and list quality. Check your spam score, monitor complaints, and clean your list.