Email Deliverability Guide: Make Sure Your Emails Reach the Inbox

What Is Email Deliverability?

Email deliverability is the ability of your emails to reach your subscribers' inboxes rather than their spam folders, promotions tabs, or being blocked entirely. You can write the best email in the world, but if it lands in spam, nobody will ever see it.

Deliverability is not binary. It exists on a spectrum. Your emails might reach 95% of inboxes, or 60%, or 30%. The difference between 95% and 60% deliverability means 35% of your email revenue disappears. For a store generating $5,000 per month from email, that is $1,750 in lost revenue every month from an invisible problem.

How Email Delivery Works

When you send an email, it goes through several checkpoints before reaching the inbox:

1. Your email platform sends the message through its mail servers.
2. The receiving mail server (Gmail, Outlook, Yahoo) checks sender authentication (SPF, DKIM, DMARC).
3. Spam filters evaluate the email's content, sender reputation, and recipient engagement history.
4. Inbox placement is determined. The email lands in the primary inbox, promotions tab, spam folder, or is rejected entirely.

Each of these stages can cause delivery failures. Optimizing deliverability means passing every checkpoint reliably.

Email Authentication: The Technical Foundation

SPF (Sender Policy Framework)

SPF tells receiving servers which mail servers are authorized to send email on behalf of your domain. Without SPF, anyone could send emails pretending to be from your domain.

How to set it up:

1. Access your domain's DNS settings (through your domain registrar like Namecheap, GoDaddy, or Cloudflare)
2. Add a TXT record with the SPF value provided by your email platform
3. Example: v=spf1 include:_spf.google.com include:sendgrid.net ~all

Your email platform provides the exact SPF record to add. This is typically a five-minute setup.

DKIM (DomainKeys Identified Mail)

DKIM adds a cryptographic signature to your emails that proves they were not altered in transit. It is like a digital seal of authenticity.

How to set it up:

1. Your email platform generates a DKIM key pair
2. Add the public key as a CNAME or TXT record in your DNS settings
3. Your platform automatically signs outgoing emails with the private key

Most email platforms provide step-by-step instructions for DKIM setup. It typically requires adding one or two DNS records.

DMARC (Domain-based Message Authentication, Reporting, and Conformance)

DMARC tells receiving servers what to do with emails that fail SPF or DKIM checks. It also provides reports on who is sending email using your domain.

How to set it up:

1. Add a TXT record to your DNS: v=DMARC1; p=none; rua=mailto:[email protected]
2. Start with p=none (monitor only) to see reports without affecting delivery
3. Once you have confirmed legitimate senders, move to p=quarantine (suspicious emails go to spam) or p=reject (suspicious emails are blocked)

Custom Sending Domain

By default, your emails are sent from your email platform's shared domain (e.g., via mailchimp.com). Setting up a custom sending domain means emails appear to come directly from your domain (e.g., mail.yourstore.com).

This improves deliverability because:

• You build your own sender reputation instead of sharing one
• Emails look more professional and trustworthy
• Authentication is cleaner with a dedicated domain

Most email platforms support custom sending domains. Follow their documentation to set up the necessary DNS records.

Sender Reputation

Your sender reputation is a score that email providers assign to your sending domain and IP address. A high reputation means your emails reach inboxes. A low reputation means spam folder or outright rejection.

Factors That Improve Reputation

High engagement: When subscribers open, click, reply, and move your emails to their primary inbox, it signals to providers that your emails are wanted.

Low bounce rate: Keep hard bounces below 2%. Clean your list regularly to remove invalid addresses.

Low spam complaints: Keep spam complaint rates below 0.1%. Even a small number of complaints relative to your send volume can damage reputation.

Consistent sending volume: Sending 1,000 emails today and 50,000 tomorrow looks suspicious. Ramp up volume gradually (increase by no more than 20-30% per day).

Authentication: Properly configured SPF, DKIM, and DMARC demonstrate legitimacy.

Factors That Damage Reputation

Purchased or scraped email lists: Sending to people who did not opt in generates spam complaints and bounces that devastate your reputation.

High unsubscribe rates: If more than 0.5% of recipients unsubscribe per campaign, your content is not matching expectations.

Spam trap hits: Spam traps are email addresses maintained by providers specifically to catch spammers. They end up on purchased lists and old, unclean lists. Hitting even one spam trap can severely damage your reputation.

Sending to disengaged subscribers: Continuing to email people who never open depletes your reputation because providers see low engagement as a sign of unwanted email.

List Hygiene Best Practices

Regular Cleaning Schedule

After every campaign: Remove hard bounces immediately. These are invalid addresses that will never deliver.

Monthly: Review soft bounces. If an address has soft-bounced three or more times, remove it.

Quarterly: Identify subscribers who have not opened or clicked any email in 90 days. Send a re-engagement campaign. Suppress those who do not respond.

Biannually: Remove all subscribers with zero engagement in 180 days. They are hurting your reputation without providing value.

Double Opt-In

Double opt-in requires new subscribers to click a confirmation link in a verification email before being added to your list. This ensures every subscriber is:

• A real person (not a bot)
• Using a valid email address
• Genuinely interested in receiving your emails

Double opt-in reduces list growth by 10-20% but dramatically improves list quality, engagement rates, and deliverability.

Sunset Policy

A sunset policy is a rule that automatically removes subscribers after a period of non-engagement:

• "If a subscriber has not opened any email in 120 days and has not purchased in 180 days, they are automatically suppressed from future campaigns."

This feels counterintuitive (you are making your list smaller) but a smaller, engaged list outperforms a larger, disengaged one every time.

Content Best Practices

Avoiding Spam Filters

Spam filters analyze your email content for patterns associated with spam:

Avoid:

• ALL CAPS in subject lines or body text
• Excessive exclamation marks (!!!)
• Spam trigger phrases: "Act now," "Limited time," "Free money," "Click here"
• Image-only emails with no text
• Misleading subject lines that do not match the content
• Excessive use of red or green colored text
• Too many links (keep to 3-5 per email)

Do:

• Write naturally as if you are emailing a friend
• Maintain a healthy text-to-image ratio (60% text, 40% images minimum)
• Include a plain-text version of every HTML email
• Use a recognizable from name and reply-to address
• Include your physical mailing address (required by CAN-SPAM)

Engagement-Driven Content

The best deliverability strategy is sending emails people actually want to read:

• Segment your list so each subscriber receives relevant content
• Personalize subject lines and content
• Provide genuine value (not just promotions)
• Make it easy to engage (clear CTAs, mobile-optimized design)
• Honor unsubscribe requests instantly

High engagement tells email providers your emails are wanted, which improves inbox placement for all future sends.

Monitoring Deliverability

Key Metrics to Watch

Delivery rate: Percentage of emails that reach the server (not bounced). Should be above 98%.

Inbox placement rate: Percentage of delivered emails that land in the inbox (not spam or promotions). Harder to measure directly but tools like GlockApps or Mailgun Inbox Placement can estimate it.

Open rate trends: A sudden drop in open rates across all campaigns often indicates a deliverability problem, not a content problem.

Bounce rate: Hard bounces above 2% or soft bounces above 5% signal list quality issues.

Spam complaint rate: Above 0.1% is a red flag. Above 0.3% is an emergency.

Tools for Monitoring

Google Postmaster Tools (free): Shows your domain's reputation with Gmail, spam rate, and authentication results. Essential for any store with Gmail subscribers (which is most stores).

Mail-Tester.com (free): Send a test email and get a score with specific recommendations. Good for checking individual emails before sending.

Your email platform's analytics: Most platforms (Klaviyo, Mailchimp, etc.) show bounce rates, spam complaints, and delivery rates per campaign.

Recovering from Deliverability Problems

If your deliverability has tanked, here is the recovery plan:

1. Immediately stop sending to your full list. Continuing to send with poor reputation makes things worse.
2. Clean your list aggressively. Remove all non-engaged subscribers from the last 90 days.
3. Fix authentication issues. Verify SPF, DKIM, and DMARC are all properly configured.
4. Start sending to your most engaged segment only. Send only to subscribers who opened an email in the last 30 days.
5. Gradually expand. Over 4-6 weeks, slowly increase your audience to include moderately engaged subscribers.
6. Monitor continuously. Watch bounce rates, spam complaints, and open rates closely during recovery.

Reputation recovery takes 4-8 weeks of consistent, clean sending. There are no shortcuts.

Key Takeaways

• Deliverability determines whether your emails are seen and poor deliverability silently erodes your email revenue
• Set up SPF, DKIM, and DMARC as the technical foundation for good deliverability
• Maintain sender reputation through high engagement, low bounces, and low spam complaints
• Clean your list quarterly by removing non-engaged subscribers and implement a sunset policy
• Monitor with Google Postmaster Tools and your platform's analytics to catch problems early
• Recovery takes 4-8 weeks of disciplined, clean sending to the most engaged segments first