Why are WordPress emails being blocked by Outlook, especially for the same domain?
Matthew Whittaker
Co-founder & CTO, Suped
Published 9 Jun 2025
Updated 17 Aug 2025
8 min read
Dealing with WordPress emails being blocked by Outlook, especially when they originate from or are sent to the same domain, is a surprisingly common frustration for website owners. You might find that emails from your WordPress site deliver perfectly fine to Gmail or other providers, but they consistently vanish when trying to reach an Outlook or Microsoft 365 inbox on your own domain. This specific issue points to a deeper problem beyond simple spam filtering, often related to how WordPress handles email by default and how Outlook's stringent security measures interpret those messages.
I've seen this scenario play out many times, and it typically stems from a combination of factors, including the native WordPress email function, inadequate email authentication, and specific security policies on the recipient's side. Even if your email service provider (ESP) reports that emails are delivered, Outlook might be silently quarantining or junking them, especially in same-domain contexts.
Understanding the root cause of WordPress email issues
The primary reason WordPress emails run into trouble is because WordPress, by default, sends emails using the PHP mail() function. This method is often insufficient for modern email deliverability standards because it lacks proper authentication. When an email server, particularly one as vigilant as Outlook (Microsoft 365), receives an email that claims to be from your domain but isn't authenticated, it views it with suspicion.
This becomes particularly problematic when you're sending to an email address on the same domain. Outlook's internal security systems are designed to prevent spoofing and phishing. If an email from info@yourdomain.com (sent via WordPress's default method) arrives at yourname@yourdomain.com (hosted on Outlook), it often triggers red flags because it didn't come through your domain's designated mail servers with proper authentication.
I've learned that a common symptom of this is when an email simply doesn't appear in the inbox, or even the spam folder, yet the sending service reports it as delivered. This is often because Outlook's internal filters (or other security layers if you're using a hosting provider like GoDaddy with a bundled Microsoft 365 account) have silently dropped or quarantined the message before it ever reached the user's mailbox, even though it technically reached their server.
The critical role of email authentication
Email authentication protocols like SPF, DKIM, and DMARC are fundamental to establishing sender legitimacy and preventing email spoofing. When your WordPress site sends emails using the default PHP function, these emails often lack proper authentication or they might be misaligned with your domain's existing authentication records. Outlook (and other major email providers) rely heavily on these records to determine if an incoming email is legitimate or potentially malicious.
SPF (Sender Policy Framework) specifies which mail servers are authorized to send emails on behalf of your domain. DKIM (DomainKeys Identified Mail) provides a cryptographic signature that verifies the email hasn't been tampered with in transit. DMARC (Domain-based Message Authentication, Reporting, & Conformance) builds on SPF and DKIM, telling receiving servers what to do with emails that fail authentication and providing valuable reports.
When WordPress sends an email directly, it often appears as if an unauthorized server is sending mail from your domain, failing authentication checks. This is particularly true for authenticated emails going to junk in Microsoft Outlook, where the problem is often a lack of proper alignment between your SPF/DKIM and the domain in the From: header.
Authentication failures
Without proper authentication, receiving servers like Microsoft Outlook will likely reject or junk messages, particularly when they appear to originate from the same domain but aren't sent through the official mail server. This is a common cause of why your emails land in spam for Outlook and Hotmail.
Common culprits behind same-domain blocking
Beyond authentication, several other factors contribute to WordPress emails being blocked, especially when targeting your own domain in Outlook.
Shared hosting IP reputation: If your WordPress site is on shared hosting, the server's IP address is used by many other websites. If any of those sites send spam, the IP could get listed on a public blocklist (or blacklist). Outlook, like other providers, checks these blocklists (blacklists) and may reject all emails from that IP, regardless of your specific domain's reputation. This can lead to your IP being blocklisted by Outlook without any direct action from your side.
Mismatching From address: WordPress often defaults to sending emails from wordpress@yourdomain.com or info@yourdomain.com depending on your site's administrator email. If this From address doesn't align with your actual email sending setup (e.g., your Microsoft 365 tenant), it can trigger spoofing alerts within Outlook's filters. This is especially relevant if your web host blocks sending emails with a From address that doesn't match the hosted domain.
Recipient-side security policies: If the Outlook recipient is within your own organization's Microsoft 365 environment, there might be internal mail flow rules, anti-spam policies, or a third-party email security solution (like Proofpoint, often bundled by hosts like GoDaddy) that are specifically quarantining or dropping emails originating from a WordPress IP, even if the domain is the same. These policies often act before the email reaches the user's inbox or even their Junk folder.
Native WordPress mail()
WordPress's default email sending method often lacks proper authentication (SPF, DKIM, DMARC), making emails appear unverified to strict email providers. It relies on the web host's server, which may have a poor IP reputation due to other users sending spam. This method is highly prone to being flagged as spam or outright blocked, especially by discerning receivers like Outlook, particularly in same-domain scenarios.
Using SMTP with an ESP
Implementing an SMTP plugin (like WP Mail SMTP) and routing your emails through a reputable email service provider (ESP) ensures that emails are sent through a legitimate mail server with proper authentication. This significantly improves your sender reputation and leads to much better deliverability and inbox placement, even for Outlook.
Example DMARC recordDNS
_dmarc.yourdomain.com IN TXT "v=DMARC1; p=none; rua=mailto:reports@yourdomain.com;"
Steps to troubleshoot and fix the issue
To fix your WordPress emails being blocked by Outlook, especially for the same domain, follow these steps:
Verify SMTP setup: The most crucial step is to abandon the default PHP mail() function. Install and configure an SMTP plugin like WP Mail SMTP and connect it to a reputable email service provider (ESP) such as Brevo (formerly Sendinblue), SendGrid, or Mailgun. Ensure the From Email setting in the plugin matches your domain's actual sending email address.
Check ESP logs and Microsoft Message Trace: If your ESP reports delivered, the problem is likely on Outlook's receiving end. For Outlook recipients on Microsoft 365, ask their IT administrator to run a message trace. This will show exactly what happened to the email after it hit their server, including if it was quarantined, moved to junk, or dropped due to internal policies.
DNS records review: Ensure your domain's SPF, DKIM, and DMARC records are correctly published and aligned. Incorrect configurations can cause emails to fail authentication. Use our free DMARC record generator tool and check your existing records using a DNS lookup tool. Microsoft has new sender requirements that heavily emphasize authentication.
Host-specific security: If your domain's email is managed by your web host (e.g., GoDaddy with bundled Microsoft 365), they might have additional security layers like Proofpoint. Check their security hub or contact support to see if your WordPress emails are being quarantined or silently dropped by these systems. You might need to add your sending domain or IP to an allowlist within their specific email filtering settings.
Domain and IP reputation: Even with an SMTP service, a poor sender reputation can lead to blocking. Regularly monitor your sending domain and IP address on major email blocklists (blacklists). Being listed can severely impact deliverability to all providers, including Outlook.
Key practices for WordPress email deliverability
SMTP usage: Always use a dedicated SMTP plugin for WordPress to route emails through a reliable email service, rather than relying on the default PHP mail() function.
Authentication: Ensure your DNS records (SPF, DKIM, DMARC) are accurately set up to authenticate your email sending domain. This is non-negotiable for Hotmail and Outlook deliverability.
Proactive monitoring: Monitor your email logs and Outlook deliverability closely for any unusual blocking or quarantining. Periodically check your domain and IP reputation on major blocklists (blacklists).
Views from the trenches
Best practices
Always use an external SMTP service for WordPress emails, do not rely on the default PHP mail() function.
Implement SPF, DKIM, and DMARC immediately for any sending domain to ensure proper email authentication.
Regularly review your Email Service Provider's logs and perform recipient-side message traces in Microsoft 365 to diagnose issues.
Common pitfalls
Ignoring bounce messages or misleading 'delivered' statuses that do not reflect actual inbox placement.
Failing to check if the web host's shared IP address is listed on any common blocklists (blacklists).
Overlooking host-specific email security measures that might silently quarantine or drop your emails.
Expert tips
For persistent Outlook deliverability issues, running a message trace in the Microsoft 365 admin center is invaluable for diagnosis.
If a transactional email service shows 'delivered' but emails are not arriving, investigate deeper into recipient-side filtering, especially with shared hosting.
Ensure that your 'From' email address in WordPress is consistent with your domain and fully authenticated through your chosen SMTP service.
Expert view
Expert from Email Geeks says: Using an SMTP plugin and an external SMTP relay is crucial, as web host IP reputation can often be poor and lead to deliverability problems.
2023-09-30 - Email Geeks
Expert view
Expert from Email Geeks says: Authentication issues or specific security settings within Microsoft 365 are very likely culprits when WordPress emails are blocked by Outlook, especially for internal domains.
2023-10-01 - Email Geeks
Solving your WordPress email deliverability
In summary, getting WordPress emails delivered to Outlook, particularly for same-domain scenarios, requires moving beyond the default PHP mail() function and embracing proper email authentication with a reliable SMTP service. By ensuring your emails are correctly authenticated with SPF, DKIM, and DMARC, and by actively monitoring deliverability from your ESP's logs and Microsoft 365 message traces, you can significantly improve your chances of reaching the inbox.
Always remember that email deliverability is a complex puzzle, and proactive identification of issues is key. Investing a little time into your WordPress email setup can save you a lot of headache down the line.
, receives an email that claims to be from your domain but isn't authenticated, it views it with suspicion.
Outlook, particularly in same-domain scenarios.
Hotmail and Outlook deliverability.
