Are your Microsoft 365 emails going to spam instead of reaching your customers’ inboxes? You’re not alone. Many businesses experience email deliverability problems even when using professional email services such as Microsoft 365 and Exchange Online.
Imagine sending an important quotation, invoice or business proposal, only to discover that your email landed in the recipient’s junk folder. This can delay communication, affect customer relationships and potentially lead to missed business opportunities.
One common reason for email delivery problems is incorrect or incomplete email authentication.
Technologies such as SPF, DKIM and DMARC help receiving mail servers verify whether messages are authorized to use your business domain.
However, email authentication is only part of the solution. Sender reputation, message content, recipient engagement and Microsoft 365 configuration can also influence inbox placement.
In this guide, we’ll explain why Microsoft 365 emails go to spam, how to configure SPF, DKIM and DMARC, and how to troubleshoot email deliverability issues for business domains.
Why Are Microsoft 365 Emails Going to Spam?
Microsoft 365 emails may reach spam folders because of failed email authentication, poor sender reputation, suspicious message content, compromised accounts or recipient-side filtering policies.
Even legitimate business emails can be classified as spam if receiving systems cannot establish sufficient trust in the sender.
Common Causes of Microsoft 365 Email Deliverability Problems
- Missing or incorrect SPF records
- DKIM signing not enabled or misconfigured
- Missing DMARC policy
- Poor domain or IP reputation
- Suspicious links or attachments
- Excessive bulk email activity
- Compromised Microsoft 365 accounts
- Email forwarding or authentication alignment issues
- Recipient spam-filtering rules
Quick Answer: If Microsoft 365 emails are going to spam, start by checking SPF, DKIM and DMARC authentication. Then review message headers, Microsoft 365 message trace, sender reputation and email content. Correct authentication problems and test delivery again.
1. What Is SPF in Microsoft 365?
SPF stands for Sender Policy Framework. It is an email authentication mechanism that identifies which mail servers are authorized to send emails for a domain.
When a receiving mail server gets a message, it can check the sender’s SPF record in DNS to determine whether the sending server is authorized.
How Does SPF Work?
Suppose your company uses Microsoft 365 to send business emails from:
employee@yourcompany.com
Your domain’s SPF record tells receiving mail systems which servers are permitted to send email on behalf of the domain used for SPF validation.
Microsoft 365 SPF Record Example
For a domain sending email only through Microsoft 365, a common SPF TXT record is:
v=spf1 include:spf.protection.outlook.com -all
This record authorizes Microsoft’s published sending infrastructure and specifies a hard-fail policy for senders not covered by the record.
How to Fix SPF Problems
- Sign in to your domain’s DNS management panel.
- Locate the existing SPF TXT record.
- Verify whether Microsoft 365 is included.
- Identify other legitimate email-sending services.
- Update the SPF record if required.
- Save the changes and allow DNS propagation.
- Test SPF authentication.
Important: A domain should not publish multiple separate SPF records. If your business uses Microsoft 365 alongside CRM software, website forms or another email platform, their authorized senders may need to be combined into one valid SPF policy.
SPF also has a DNS lookup limit, so avoid adding unnecessary mechanisms.
2. What Is DKIM in Microsoft 365?
DKIM stands for DomainKeys Identified Mail.
It adds a cryptographic signature to outgoing emails so receiving systems can verify that selected message content and headers have not been modified after signing.
DKIM also helps establish that the message was signed using a key associated with the signing domain.
Why Is DKIM Important?
Without properly configured DKIM, receiving systems have less authentication evidence available when evaluating messages.
DKIM is especially useful because a valid signature can sometimes survive forwarding when the signed content remains unchanged.
However, DKIM does not guarantee inbox placement.
How to Enable DKIM in Microsoft 365
- Open the Microsoft Defender portal.
- Navigate to the DKIM configuration area under email authentication settings.
- Select your custom business domain.
- Review the required DNS CNAME records.
- Add the records through your DNS provider.
- Wait for DNS propagation.
- Enable DKIM signing for the domain.
- Send a test email and verify the authentication result.
Microsoft 365 commonly uses two DKIM selectors for custom-domain configuration.
The exact CNAME target values depend on your tenant and domain configuration. Always copy them from the Microsoft 365 administration interface rather than using example values from unrelated websites.
3. What Is DMARC and Why Does Your Business Need It?
DMARC stands for Domain-based Message Authentication, Reporting and Conformance.
It builds on SPF and DKIM to help domain owners define how receiving systems should handle messages that fail DMARC authentication checks.
DMARC also provides reporting capabilities that help businesses identify legitimate and potentially unauthorized email sources.
How Does DMARC Work?
DMARC checks whether a message passes SPF or DKIM with the required domain alignment.
A message can pass DMARC when at least one of these authentication methods passes and aligns with the domain in the visible From address.
Example DMARC Record
A basic monitoring-only DMARC record looks like this:
v=DMARC1; p=none; rua=mailto:dmarc-reports@yourcompany.com
This policy requests aggregate DMARC reports without asking receiving systems to quarantine or reject failing messages.
The reporting mailbox must be configured appropriately. External reporting destinations may require additional authorization.
DMARC Policy Options
| Policy | Meaning |
| p=none | Monitor authentication without requesting enforcement |
| p=quarantine | Request suspicious failing messages be treated as spam |
| p=reject | Request rejection of messages failing DMARC |
Receiving email systems ultimately determine how they apply these policies.
How to Fix DMARC Problems
Begin with a monitoring policy and review the reports.
Identify every legitimate email-sending source, including Microsoft 365, CRM systems, website applications and third-party platforms.
Ensure those services can pass aligned SPF or DKIM authentication.
After validating legitimate senders, consider moving gradually toward stronger enforcement.
Do not immediately configure p=reject without checking all authorized email sources, because legitimate messages could be rejected.
4. SPF vs DKIM vs DMARC: What’s the Difference?
Although SPF, DKIM and DMARC work together, each performs a different function.
| Feature | SPF | DKIM | DMARC |
| Primary purpose | Authorize sending servers | Verify message signatures | Check alignment and apply domain policy |
| DNS configuration | TXT record | Public key records, commonly configured through CNAMEs in Microsoft 365 | TXT record |
| Helps prevent spoofing | Yes, within its scope | Yes, when validated and aligned | Yes, through alignment and policy |
| Supports reporting | Limited | Limited | Aggregate and optional forensic reporting |
| Guarantees inbox delivery | No | No | No |
For reliable Microsoft 365 email authentication, businesses should configure all three correctly.
5. How to Check SPF, DKIM and DMARC Records
Before changing DNS settings, verify your current email authentication configuration.
You can use DNS lookup tools or command-line utilities.
Check SPF Using Windows
Open Command Prompt and run:
nslookup -type=TXT yourcompany.com
Look for a TXT record beginning with:
v=spf1
Check DMARC
Run:
nslookup -type=TXT _dmarc.yourcompany.com
Look for a record beginning with:
v=DMARC1
Check DKIM
For Microsoft 365, review the two selector CNAME records shown in your tenant’s DKIM configuration.
You can query them using:
nslookup -type=CNAME selector1._domainkey.yourcompany.com
Repeat the test for selector2.
Replace the example domain with your actual business domain.
A DNS record being present does not necessarily mean email authentication is passing. Always verify the results from an actual delivered message.
6. How to Check Microsoft 365 Email Headers
Email headers provide useful information when investigating why messages are being classified as spam.
Send a test email to an external mailbox and inspect the full message headers.
Look for authentication results such as:
spf=pass
dkim=pass
dmarc=pass
These values indicate that the corresponding authentication checks passed for that message.
However, passing authentication does not guarantee that the message will reach the inbox.
Also review the sending domain, message routing and any spam-related information supplied by the receiving system.
If the message was forwarded, remember that forwarding can affect SPF results.
7. Check Microsoft 365 Message Trace
Microsoft 365 administrators can use message trace to investigate email delivery.
Message trace helps identify whether Exchange Online processed, delivered, deferred or rejected a message.
How to Check Message Trace
- Open the Exchange admin center.
- Navigate to Mail flow.
- Open Message trace.
- Search using the sender, recipient and time range.
- Review the message status and available details.
Message trace is useful for investigating Exchange Online transport behavior.
However, a message marked as delivered may still have been placed in the recipient’s spam folder by the destination system.
For external recipients, additional investigation may be required.
8. Check Sender Reputation and Email Content
Even when SPF, DKIM and DMARC are configured correctly, emails may still be filtered as spam.
Receiving systems consider several additional signals.
Sender Reputation
Domains and sending IP addresses associated with abusive email activity may experience reduced deliverability.
Businesses should avoid sending unsolicited bulk messages and investigate unusual outbound email activity.
Email Content
Messages containing suspicious links, misleading subject lines or unexpected attachments may trigger spam filtering.
Use clear subject lines, legitimate business information and trustworthy links.
Recipient Engagement
Email providers may also consider recipient interactions and historical sending patterns.
For marketing campaigns, maintain appropriate consent and unsubscribe practices.
Compromised Accounts
If an attacker gains access to a Microsoft 365 mailbox, unauthorized messages may damage sender reputation.
Investigate suspicious sign-ins, unexpected forwarding rules and unusual sending behavior.
9. Microsoft 365 Emails Going to Gmail Spam: What to Check
Some businesses report that their Microsoft 365 messages reach Outlook recipients successfully but appear in Gmail spam folders.
This does not automatically mean Microsoft 365 is malfunctioning.
Different email providers use different filtering systems.
Troubleshooting Steps
- Verify SPF authentication.
- Confirm DKIM signing for the custom domain.
- Check DMARC alignment.
- Review the Gmail message’s authentication results.
- Examine sending patterns and message content.
- Check whether the domain has a history of unwanted email.
For businesses sending significant volumes to Gmail, review Google’s current sender requirements and relevant Postmaster Tools information.
Avoid asking recipients to disable spam protection as a general solution.
10. How to Prevent Microsoft 365 Emails From Going to Spam
Businesses should establish a consistent email authentication and security process.
Recommended practices include:
- Maintain one valid SPF record.
- Enable DKIM signing for custom domains.
- Configure and monitor DMARC.
- Review third-party email senders.
- Protect Microsoft 365 accounts with multifactor authentication.
- Monitor suspicious sign-ins and outbound email activity.
- Maintain accurate DNS records.
- Follow responsible email marketing practices.
- Investigate delivery complaints promptly.
A properly configured email authentication system improves domain protection and gives receiving systems stronger evidence about legitimate messages.
However, no configuration can guarantee 100% inbox delivery.
Microsoft 365 Email Support in Noida – ATAOP
Businesses experiencing recurring email delivery problems may need technical assistance with DNS configuration, Microsoft 365 administration and email authentication.
ATAOP (OPC) Private Limited is an IT support company serving Noida, Greater Noida, Delhi NCR and businesses across India.
ATAOP provides IT infrastructure and managed IT support services, including assistance with Microsoft 365-related technical issues.
For businesses facing email authentication failures, Outlook connectivity problems or domain configuration challenges, a structured assessment can help identify the underlying issue.
Whether you’re configuring Microsoft 365 for a new business domain or troubleshooting existing email services, proper authentication and security settings are essential.
Visit https://ataop.com/ to discuss your business IT support requirements.
Frequently Asked Questions
Why are my Microsoft 365 emails going to spam?
Common causes include failed SPF, DKIM or DMARC authentication, poor sender reputation, suspicious content and recipient-side filtering policies.
Does SPF prevent Microsoft 365 emails from going to spam?
SPF helps receiving servers identify authorized senders, but it does not guarantee inbox placement. DKIM, DMARC and other deliverability factors also matter.
Is DKIM required for Microsoft 365?
DKIM signing is strongly recommended for custom business domains because it supports email authentication and DMARC alignment.
What happens if DMARC is not configured?
Without DMARC, your domain lacks a published DMARC policy and its associated reporting capabilities. Receiving systems may still apply their own spam and security checks.
How long do SPF, DKIM and DMARC changes take?
DNS changes may become visible within minutes or take longer depending on caching and DNS TTL settings. Always verify propagation before concluding that configuration changes have failed.
Can Microsoft 365 emails go to spam even when SPF, DKIM and DMARC pass?
Yes. Email providers also evaluate sender reputation, message content, sending behavior and other filtering signals.
Can ATAOP help with Microsoft 365 email issues in Noida?
ATAOP provides business IT support and Microsoft 365-related technical assistance for organizations in Noida, Greater Noida and Delhi NCR.
