Why Are My Emails Going to Spam?

Editorial Team·1 months ago

021014 minutes read

Quick answer: Emails going to spam is most often caused by missing or misconfigured SPF, DKIM, or DMARC authentication records, a poor sender reputation from high bounce or complaint rates, or content patterns that trigger spam filters. Checking authentication records with a tool like MXToolbox or mail-tester.com is the fastest first step to diagnosing the cause.

"My Emails Are Landing in Spam" — Why It Happens and How to Fix It

A situation that comes up regularly for anyone who sends email from a custom domain: messages that should be arriving in the recipient's inbox are instead landing in the spam folder. The sender may not know this is happening until a recipient mentions it, or until a response that should have arrived does not. The problem is particularly frustrating because the messages look correct from the sender's side — they send without errors, and there is no indication that anything went wrong. The issue is not with the message itself but with how recipient mail servers are evaluating the sender's trustworthiness. This guide covers the most common reasons emails go to spam and the steps to fix each one — from DNS authentication records to sender reputation to content patterns. The specific behavior of spam filters varies by email provider and changes over time as providers update their filtering algorithms; the principles described here reflect current best practice as of mid-2026, and testing with a tool like mail-tester.com before and after making changes is the most reliable way to confirm improvement.

How Spam Filters Decide Where Email Goes

Modern spam filters do not rely on a single signal to classify email. They evaluate dozens of factors simultaneously and assign a composite score that determines whether a message is delivered to the inbox, the spam folder, or rejected outright. The three primary categories of signals are authentication (does the message come from a server authorized to send for this domain?), reputation (does the sending domain and IP address have a history of sending legitimate email?), and content (does the message contain patterns associated with spam?). Authentication and reputation signals carry more weight than content signals in most modern spam filters — a message from a well-authenticated sender with a strong reputation will typically reach the inbox even if the content is imperfect, while a message from an unauthenticated sender with a poor reputation will often be filtered regardless of content quality. The shift toward authentication-based filtering has accelerated in recent years. Google and Yahoo announced in 2024 that bulk senders must have SPF, DKIM, and DMARC configured to send to Gmail and Yahoo Mail addresses — senders without these records face increased filtering or outright rejection. Microsoft has implemented similar requirements for Outlook and Microsoft 365. For anyone sending email from a custom domain, configuring these three DNS records is no longer optional for reliable deliverability.

Why Emails Go to Spam — 5 Common Causes and Fixes

CauseSignal TypeFixMissing SPF recordAuthenticationAdd SPF TXT record to DNSMissing or invalid DKIMAuthenticationConfigure DKIM at sending provider; publish key in DNSNo DMARC policyAuthenticationAdd DMARC TXT record; start with p=nonePoor sender reputationReputationClean list; reduce bounces and complaintsSpam-trigger contentContentTest with mail-tester.com; revise subject and body

1. Missing or Misconfigured SPF Record

SPF (Sender Policy Framework) is a DNS TXT record that lists the mail servers authorized to send email for a domain. When a recipient mail server receives a message claiming to be from example.com, it checks the SPF record for example.com to verify that the sending server is on the authorized list. If there is no SPF record, or if the sending server is not listed in the SPF record, the message fails SPF authentication — which increases the likelihood of spam placement. A common scenario is a business that switches email providers but forgets to update the SPF record to include the new provider's mail servers, causing messages from the new provider to fail SPF. Checking the SPF record for a domain takes less than a minute using a tool like MXToolbox (mxtoolbox.com/spf.aspx) or Google Admin Toolbox (toolbox.googleapps.com/apps/checkmx). These tools show the current SPF record and flag common errors such as missing includes, too many DNS lookups (the SPF specification limits lookups to 10), or a missing "all" mechanism. The email provider's documentation specifies the exact SPF include statement to add — for Google Workspace, it is "include:_spf.google.com"; for Microsoft 365, it is "include:spf.protection.outlook.com." Adding the correct include and publishing the updated SPF record typically takes effect within a few hours.

2. Missing or Invalid DKIM Signature

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing messages. The sending server signs each message with a private key, and the corresponding public key is published in DNS as a TXT record. Recipient servers use the public key to verify that the message was signed by the sending domain and was not altered in transit. A message without a DKIM signature, or with an invalid signature, fails DKIM authentication — which, combined with a DMARC policy, can result in the message being marked as spam or rejected. DKIM is configured at the email sending provider — the provider generates the key pair and provides the public key to be added to DNS. For Google Workspace, DKIM setup is done in the Google Admin console under Apps > Google Workspace > Gmail > Authenticate email. For Microsoft 365, DKIM is configured in the Microsoft 365 Defender portal under Email & Collaboration > Policies & Rules > Threat Policies > DKIM. After generating the key, the public key must be added to the domain's DNS as a TXT record — the provider's documentation specifies the exact record name and value. Verifying DKIM after setup using a tool like MXToolbox or mail-tester.com confirms that the signature is being applied correctly.

3. Missing or Permissive DMARC Policy

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a DNS TXT record that tells recipient servers what to do with messages that fail SPF or DKIM checks. A DMARC policy of "p=none" instructs recipient servers to take no action on failing messages but to send reports to the domain owner — useful for monitoring without affecting deliverability. A policy of "p=quarantine" instructs recipient servers to place failing messages in the spam folder. A policy of "p=reject" instructs recipient servers to reject failing messages outright. Without a DMARC record, recipient servers make their own decisions about failing messages — and many treat the absence of DMARC as a signal of lower trustworthiness. For domains that do not yet have DMARC configured, starting with "p=none" and a reporting address is the recommended approach: it provides visibility into which servers are sending email on behalf of the domain without risking legitimate messages being rejected. After reviewing the DMARC reports and confirming that all legitimate sending sources are covered by SPF and DKIM, the policy can be moved to "p=quarantine" and eventually "p=reject." A basic DMARC record looks like: `v=DMARC1; p=none; rua=mailto:dmarc-reports@example.com` — published as a TXT record at `_dmarc.example.com`.

4. Poor Sender Reputation

Sender reputation is a score assigned to a sending domain and IP address based on historical sending behavior. High bounce rates (messages sent to invalid or non-existent addresses), high spam complaint rates (recipients clicking "Mark as Spam"), and sudden large increases in sending volume from a new domain all damage sender reputation. A new domain with no sending history starts with a neutral reputation — recipient mail servers are cautious about messages from domains they have not seen before, which is why new domains often experience higher spam placement rates initially. Improving sender reputation requires addressing the underlying causes: clean the recipient list to remove invalid addresses (use an email verification service before sending to a large list), reduce spam complaint rates by sending only to recipients who have explicitly opted in and by making unsubscribing easy, and warm up new domains gradually by starting with small sending volumes and increasing over days or weeks. Google Postmaster Tools (postmaster.google.com) provides domain reputation data for messages sent to Gmail addresses — checking this dashboard after making changes shows whether reputation is improving. Microsoft's Smart Network Data Services (SNDS) provides similar data for messages sent to Outlook and Microsoft 365 addresses.

5. Content Patterns That Trigger Spam Filters

⚠️ Worth testing before sending: Content filtering is less deterministic than authentication and reputation signals, but certain patterns consistently increase spam scores across major providers. Subject lines with all-caps words, excessive punctuation (!!!), or phrases commonly associated with spam (free, urgent, act now, guaranteed, no obligation) are flagged by many filters. Message bodies with a high ratio of images to text, many hyperlinks relative to the message length, or links to domains with poor reputation also increase spam scores. HTML email with broken or missing plain-text alternatives is another common trigger. Testing messages with mail-tester.com before sending provides a spam score out of 10 and identifies specific content issues — a score of 8 or above is generally considered good for deliverability. Addressing the specific issues flagged by the test is more effective than guessing which content elements are causing the problem.

Step-by-Step: How to Fix Emails Going to Spam

Step 1: Check Authentication Records with MXToolbox

Go to mxtoolbox.com and use the Email Health tool or the individual SPF, DKIM, and DMARC lookup tools to check the current authentication records for the sending domain. The tool flags missing records, common misconfigurations, and SPF lookup limit violations. Note any issues identified — these are the highest- priority fixes, as authentication failures are the most common cause of spam placement for custom domain senders. If SPF, DKIM, or DMARC records are missing or misconfigured, fix these before investigating other causes.

Step 2: Configure or Correct SPF, DKIM, and DMARC

Follow the email provider's documentation to configure SPF, DKIM, and DMARC for the sending domain. For Google Workspace: SPF is added as a TXT record containing "include:_spf.google.com ~all"; DKIM is generated in the Admin console and the public key is added to DNS; DMARC is added as a TXT record at _dmarc.[domain]. For Microsoft 365: SPF includes "include:spf.protection.outlook.com"; DKIM is configured in the Microsoft 365 Defender portal; DMARC is added at _dmarc.[domain]. After adding or updating records, wait for DNS propagation (typically a few hours) and verify using MXToolbox or mail-tester.com.

Step 3: Test a Message with mail-tester.com

Go to mail-tester.com, which generates a unique test email address. Send a representative message to that address — using the same sending tool, template, and from address that is experiencing spam placement. After sending, click "Check your score" on the mail-tester.com page to see the spam score and a detailed breakdown of authentication results, content issues, and blacklist status. Address the specific issues identified, starting with authentication failures (which have the highest impact) and then content issues. Re-test after making changes to confirm improvement.

Step 4: Check Sender Reputation and Blacklist Status

Check whether the sending domain or IP address is listed on any email blacklists using MXToolbox's blacklist check (mxtoolbox.com/blacklists.aspx). A blacklist listing is a strong signal that the sending domain or IP has been associated with spam in the past — either through actual spam sending, a compromised account, or a shared IP address used by other senders with poor practices. If the domain or IP is blacklisted, follow the delisting process for each blacklist (each has its own process). Check Google Postmaster Tools for domain reputation data for Gmail deliverability, and Microsoft SNDS for Outlook deliverability.

Step 5: Ask Recipients to Mark as Not Spam and Add to Contacts

For messages that are already landing in spam for specific recipients, asking those recipients to mark the message as "Not Spam" (or "Not Junk") and to add the sending address to their contacts is the most direct fix for that recipient's inbox. This action signals to the recipient's email provider that messages from the sender are wanted, which improves deliverability for future messages to that recipient. It does not fix the underlying authentication or reputation issues — those require the DNS and sending practice changes described in the previous steps — but it provides an immediate workaround for recipients who need to receive messages while the underlying issues are being resolved.

Frequently Asked Questions — Emails Going to Spam

Why are my emails going to spam?

The most common causes are missing or misconfigured SPF, DKIM, or DMARC authentication records, a poor sender reputation from high bounce or complaint rates, or content patterns that trigger spam filters. Checking authentication records with MXToolbox and testing messages with mail-tester.com identifies the specific cause quickly.

What is SPF, DKIM, and DMARC, and why do they matter?

SPF lists the mail servers authorized to send for a domain. DKIM adds a cryptographic signature that verifies the message was not altered in transit. DMARC tells recipient servers what to do with messages that fail SPF or DKIM. Together, these three records are the foundation of email authentication — missing or misconfigured records are one of the most common reasons legitimate email lands in spam.

Does sender reputation affect whether emails go to spam?

Yes. Reputation is influenced by bounce rates, spam complaint rates, sending volume patterns, and the age and history of the sending domain and IP. A new domain with no sending history is treated with more suspicion than an established domain. Google Postmaster Tools and Microsoft SNDS provide reputation data for messages sent to Gmail and Outlook addresses respectively.

Can email content cause messages to go to spam?

Yes, though content filtering is less deterministic than authentication and reputation signals. All-caps subject lines, spam-associated phrases, high image-to-text ratios, and many links relative to message length increase spam scores. Testing with mail-tester.com before sending provides a score and identifies specific content issues.

How do I get my emails out of the spam folder?

The most effective steps: verify and correct SPF, DKIM, and DMARC records; reduce bounce rates by cleaning the recipient list; ask recipients to mark messages as "Not Spam" and add the sending address to their contacts; avoid content patterns that trigger filters; and warm up new sending domains gradually. For bulk or transactional email, using a reputable email sending service improves deliverability.

Conclusion & My Take

Emails going to spam is almost always a solvable problem once the cause is identified — and the cause is almost always one of three things: authentication records that are missing or misconfigured, a sender reputation that has been damaged by high bounces or complaints, or content patterns that trigger filters. Authentication is the highest-priority fix because it is binary — either the records are correct or they are not — and because major providers have made it a requirement for reliable deliverability. Fixing SPF, DKIM, and DMARC resolves the majority of spam placement issues for custom domain senders. Sender reputation takes longer to improve than authentication — it is built over time through consistent sending practices, low bounce rates, and low complaint rates. For new domains, warming up gradually (starting with small volumes and increasing over weeks) is the most reliable way to establish a positive reputation. For established domains with a damaged reputation, identifying and addressing the source of the damage — a compromised account, a purchased list, or a misconfigured sending tool — is the necessary first step before reputation can recover. Have you resolved a spam deliverability problem that was caused by something not covered here, or found a particular tool or approach that was especially effective? Spam filter behavior varies by provider and changes over time — feel free to share your experience in the comments below.