Email Deliverability: Why Your Emails Land in Spam and How to Fix It
Email deliverability is the measure of how reliably your emails reach the inbox rather than the spam folder, promotions tab, or getting blocked entirely. A campaign with a 95% open rate potential means nothing if only 60% of your emails are actually delivered to the inbox. Every other email marketing effort depends on this foundation.
Most deliverability problems are fixable, but they require understanding what inbox providers actually evaluate — and it is more than just spam trigger words.
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How Email Deliverability Works
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Inbox providers like Gmail, Outlook, and Yahoo use a combination of technical signals, sender reputation, and engagement data to decide where each incoming email is placed. The decision happens within milliseconds of the email arriving at their servers.
The four primary factors that determine email deliverability:
Domain authentication — technical records that prove the email was sent by an authorized sender
Sender reputation — the score inbox providers assign your domain based on historical sending behavior
List quality — the proportion of valid, engaged addresses on your list
Content signals — patterns in your email content that resemble known spam
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A problem in any one of these areas can send your emails to spam even if the other three are clean. Diagnosing deliverability issues requires checking all four.
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Domain Authentication: SPF, DKIM, and DMARC
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Authentication records tell receiving servers that your emails are genuinely from your domain and have not been tampered with in transit. Without them, inbox providers have no way to verify your identity and are more likely to treat your emails as suspicious.
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SPF (Sender Policy Framework)
An SPF record lists the IP addresses and services authorized to send email on behalf of your domain. When an email arrives claiming to be from your domain, the receiving server checks your DNS for an SPF record and verifies that the sending IP is on the list.
Setting up SPF: Add a TXT record to your domain's DNS settings. Your email platform will provide the specific record value. It looks like: v=spf1 include:youremailplatform.com ~all
DKIM (DomainKeys Identified Mail)
DKIM adds a cryptographic signature to outgoing emails. The receiving server checks the signature against a public key stored in your DNS to verify that the email was not altered in transit.
Setting up DKIM: Your email platform generates a DKIM key pair and provides you with a DNS record to add. This is typically a CNAME or TXT record.
DMARC (Domain-based Message Authentication, Reporting, and Conformance)
DMARC builds on SPF and DKIM by specifying what to do with emails that fail authentication — reject them, quarantine them, or allow them through. It also sends reports of authentication failures to an email address you specify, giving you visibility into who is sending email using your domain.
A basic DMARC record: v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com
All three records should be configured before sending any significant volume. Most email platforms provide step-by-step instructions for adding these records to your domain registrar.
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Sender Reputation
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Sender reputation is the score inbox providers assign your sending domain based on behavioral signals over time. Unlike a credit score, you cannot request your reputation directly — but you can infer it from deliverability outcomes and from third-party tools.
Factors that damage sender reputation:
High spam complaint rates — above 0.1% will trigger warnings; above 0.3% will cause Gmail to begin filtering your emails
Hard bounces — sending to invalid addresses signals poor list hygiene
Low engagement — emails that are consistently ignored (not opened, not clicked) signal that recipients do not want them
Sudden volume spikes — dramatically increasing your send volume without a warm-up period looks suspicious
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Factors that build sender reputation:
Consistent send volume and cadence
High engagement relative to your list size
Low bounce and complaint rates
Sending to a clean, permission-based list
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If your sender reputation has been damaged, it can be rebuilt — but it takes time. A 60–90 day period of clean, consistent sending to a highly engaged segment is the most reliable rehabilitation strategy.
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List Quality and Email Deliverability
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A list full of inactive, invalid, or disengaged addresses drags down every deliverability metric. Inbox providers notice that a significant portion of your emails are being ignored and adjust your placement accordingly.
Three list quality issues that directly harm email deliverability:
Hard bounces — emails that cannot be delivered because the address does not exist. Any address that hard bounces should be removed immediately. Bounce rates above 2% will cause most email platforms to flag your account.
Spam traps — email addresses that appear to be legitimate but are operated by inbox providers or anti-spam organizations to identify senders with poor list hygiene. There are two types: pristine spam traps (addresses that have never been real) and recycled spam traps (formerly real addresses that have been deactivated and repurposed). Hitting a spam trap indicates that your list was not built with proper permission practices.
Low engagement at scale — if 40% of your list never opens your emails, you are essentially sending to a large segment of people who have opted out in behavior if not in name. Segment and suppress low-engagement contacts before they affect your overall reputation.
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Content Signals That Trigger Spam Filters
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Modern spam filters are not primarily triggered by individual words — they evaluate content patterns, structure, and context. That said, certain content characteristics increase spam filter risk:
HTML-heavy emails with minimal text (high image-to-text ratio)
Emails that consist entirely of one large image
Excessive exclamation marks and capitalization
Certain phrases associated with spam when combined with other signals: "act now," "limited time offer," "free money"
Mismatched links (link text says one URL, the href points to another)
Broken HTML or very large HTML files
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The most reliable content approach for deliverability is also the best approach for engagement: write emails primarily in text, keep HTML clean and minimal, use accurate link text, and avoid formatting that mimics known spam patterns.
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How to Diagnose a Deliverability Problem
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If you suspect a deliverability issue — declining open rates, direct feedback from subscribers that emails are going to spam — run through this diagnostic sequence:
Check authentication — use MXToolbox or Mail-Tester to verify SPF, DKIM, and DMARC are correctly configured
Check your sending IP reputation — use Sender Score (senderscore.org) or Google Postmaster Tools to see how your domain and IP are rated
Review recent bounce and complaint rates — log into your email platform and pull the last 10 sends
Check for spam trap hits — your email platform should alert you if your list contains known spam traps
Test inbox placement — tools like GlockApps or Mail-Tester send your email to seed addresses across major providers and report where it landed
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Blakfy sets up email authentication infrastructure and deliverability monitoring for businesses that want their campaigns to reach the inbox consistently.
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Frequently Asked Questions
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Why are my emails going to the Gmail Promotions tab instead of the inbox?
The Promotions tab is not the spam folder — emails placed there are still delivered and can still be opened. For marketing emails, Promotions tab placement is expected behavior. If your goal is primary inbox placement, send plain-text or minimal-HTML emails with high personalization and a personal "from" name.
Can using certain words get my emails sent to spam?
Specific words rarely trigger spam filters on their own. Spam filters evaluate combinations of signals — content patterns, sender reputation, authentication status, and engagement history. A word like "free" in an email from a trusted sender with high engagement will not cause deliverability problems.
How long does it take to recover from poor deliverability?
Typically 60–90 days of clean sending practices before inbox providers begin restoring normal placement. This requires: fixing authentication issues, cleaning the list, suppressing inactive subscribers, and sending only to your most engaged segment during the recovery period.
Do I need a dedicated IP address for better deliverability?
For most businesses sending under 100,000 emails per month, a shared IP address through a reputable email platform is appropriate. Dedicated IPs require careful warm-up periods and are only beneficial if you have sufficient volume to maintain consistent sending — irregular senders on dedicated IPs often have worse deliverability than those on reputable shared infrastructure.
