Email Deliverability Checklist: 10 Steps to Land in the Inbox

Getting your email into the inbox requires more than a good subject line. It requires a solid infrastructure. This checklist covers the ten steps you need to take to ensure your emails land where they belong.

1. Set Up SPF, DKIM, and DMARC

Email authentication is the foundation of deliverability. Without SPF, DKIM, and DMARC, your emails are more likely to be flagged as spam or spoofed.

SPF (Sender Policy Framework) lets you specify which IPs are allowed to send email for your domain. Publish an SPF TXT record in your DNS that lists all authorized sending IPs. A common mistake is forgetting to include all ESPs you use. If you send via multiple platforms, each IP range must be in the SPF record. Keep the lookup limit of 10 DNS queries in mind. Use an SPF flattening tool if needed.

DKIM (DomainKeys Identified Mail) adds a digital signature to your emails. Your email service provider gives you a DKIM public key to add to your DNS. Sign all outgoing email with the private key. Watch for selector changes when you switch ESPs. A misaligned DKIM selector can break authentication. Verify your DKIM signature is valid by checking the header in a test email.

DMARC (Domain-based Message Authentication, Reporting, and Conformance) tells receiving servers what to do if SPF or DKIM fails. Start with a policy of p=none to monitor, then move to p=quarantine or p=reject once you are confident. Ensure your DNS record also includes a rua tag for aggregate reports and ruf for forensic reports. Parse these reports to identify unauthorized senders. DMARC alignment requires the domain in the From header to match the domain used in SPF or DKIM. Check for subdomain or third-party sending issues.

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

2. Monitor Your Sender Reputation

Sender reputation is a score that ISPs assign to your sending IP and domain. A poor reputation leads to the spam folder or outright blocking.

Sign up for Postmaster Tools from Gmail, Microsoft, and Yahoo to check your reputation. Also monitor blacklists like Spamhaus and Barracuda. If you appear on a blacklist, investigate the cause immediately. Common causes include spam complaints from old lists or compromised sending credentials. Check both your IP and domain reputation separately. A clean domain but dirty IP still hurts. Use reputation monitoring tools like SenderScore or Talos Intelligence. Track trends over time, not just daily snapshots.

3. Warm Up New IPs Gradually

When you switch to a new sending IP address or platform, you must warm it up. Start by sending small volumes to your most engaged subscribers. Increase volume by no more than 20-30% per day over two to four weeks.

Avoid sending to your full list on day one. ISPs treat sudden traffic from new IPs as suspicious. A gradual ramp builds a positive history. Segment your list: send first to those who opened in the last 30 days, then extend to less engaged. Monitor bounce rates and complaint rates during warm-up. If either spikes, pause the ramp and investigate. Some ESPs offer shared IP pools that are already warm, but dedicated IPs require full warm-up.

4. Clean Your Email List Regularly

List hygiene directly affects bounce rates and engagement metrics. Remove hard bounces immediately. Suppress addresses that have consistently soft-bounced after three attempts.

Segment out inactive subscribers—those who haven’t opened or clicked in three to six months. Send them a re-engagement campaign, then remove non-responders. A clean list improves both reputation and deliverability. Use a sunset policy: define a timeframe (e.g., 6 months) after which you stop mailing inactive contacts. Validate new signups with double opt-in to prevent typos or fake addresses. Regularly run your list through an email validation service to catch role addresses (e.g., info@, admin@).

5. Manage Bounces Properly

Hard bounces (invalid addresses) should be removed from your list on the first occurrence. Soft bounces (temporary issues like full inbox) can be retried once or twice, then suppressed if they persist.

Some ESPs automatically handle bounces, but you should double-check the settings. Set clear thresholds: for example, suppress after three soft bounces within one month. Never mail to known bad addresses. Differentiate between transient (temporary) and permanent bounces in your data. Log bounce reasons from SMTP codes (e.g., 550, 450) to identify patterns. A sudden spike in bounces could indicate a list issue or a DNS misconfiguration.

6. Align Your Sending Volume and Frequency

Consistency matters. Sending 100,000 emails one day and 5,000 the next can trigger spam filters. Keep your volume predictable. If you need to increase volume, do it gradually over several days.

Also ensure you’re sending at a frequency your subscribers expect. If you’ve sent weekly for a year, don’t suddenly send daily. Let subscribers set their preferences if possible. Monitor your sending pattern over weeks, not just days. A steady increase is safer than a spike. Also watch your sending time: sending at the same hour each batch helps build a pattern ISPs trust. If you pause sends for a holiday, ramp back up gradually.

7. Craft Relevant, Engaging Content

ISPs monitor engagement: opens, clicks, replies, and forwards. Emails that get low engagement are more likely to be filtered as spam.

Write subject lines that are clear and honest. Avoid spam trigger words like “free” or “guaranteed” in excess. Personalize where you can. Segment your list based on behavior or interests so each email is relevant. The more your recipients want your email, the better your deliverability. A/B test subject lines and content to find what resonates. Include a clear call to action that matches the email’s purpose. Avoid excessive images and ensure a text-to-image ratio of at least 60:40. Add a plain-text version for better rendering and accessibility.

8. Monitor Engagement and Spam Complaints

Track your open rate, click-through rate, and spam complaint rate. An open rate below 15% or a complaint rate above 0.1% is a red flag.

Check your email analytics weekly. If engagement drops on a particular segment, review the content relevance to that group. If complaint rates spike, pause sends to that list and investigate the source. A high complaint rate will quickly ruin your reputation. Set up feedback loops with major ISPs (Gmail, Yahoo, Outlook) to receive complaint data automatically. Use that data to remove complainers rapidly. Also track forward and reply rates as positive signals.

9. Test Deliverability Before Campaigns

Before sending a campaign, test your deliverability with tools like Mail-Tester or GlockApps. Send a test to a seed list of addresses from different ISPs and check whether they land in inbox, spam, or are blocked.

Also check your email content against common spam filters. Avoid excessive images, missing alt text, and overly salesy language. Testing catches problems before they affect your whole list. Run tests at different times of day to see if timing affects placement. Test different versions of your email to compare inbox rates. Check your email’s raw headers for authentication results (SPF, DKIM, DMARC). A test that fails authentication means you have a DNS or configuration issue.

10. Audit Your Setup Quarterly

Email infrastructure changes: you may add new sending IPs, change ESPs, or update DNS records. Schedule a quarterly review of your authentication records, list hygiene, bounce handling, and reputation.

Use the Email Deliverability Audit: A Step-by-Step Guide for Marketers to guide your review. Also check for any new standards or ISP requirements. Staying current prevents surprises. Go beyond the basics: review your DMARC policy progression, verify DKIM key rotation, and confirm no old SPF include entries are leftover. Check your sending infrastructure for any unauthorized third-party use. Perform a full deliverability test from scratch each quarter to catch regressions.

For a broader introduction to these concepts, refer to Email Deliverability: A Beginner’s Guide for B2B Marketers.

Frequently asked questions

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

Setting up SPF, DKIM, and DMARC authentication is the most critical step. Without these, your emails lack proof of legitimacy and are more likely to be filtered as spam. Start there, then move through the other steps like list hygiene and content relevance.

How often should I clean my email list?

Clean your list at least every three months. Remove hard bounces immediately and soft bounces after a few attempts. For inactive subscribers, run a re-engagement campaign every six months and remove non-responders. Regular cleaning keeps bounce rates low and engagement high.

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

Warming up a new IP typically takes two to four weeks. Start by sending small volumes (e.g., 50-100 emails per day) to your most engaged subscribers. Gradually increase volume by 20-30% daily. Rushing this process risks being blocked by ISPs.

What is a good spam complaint rate?

A good spam complaint rate is below 0.1% (less than one complaint per 1,000 emails). Rates above 0.1% signal to ISPs that your content may be unwanted. If you exceed this, review your list quality and content relevance immediately.

Do I need DMARC if I already have SPF and DKIM?

Yes. SPF and DKIM authenticate emails individually, but DMARC tells receiving servers how to handle failures. Without DMARC, spoofers can still send email that passes SPF or DKIM. DMARC gives you control and reporting to detect abuse.