Why would my emails land in Office 365 spam but not in Gmail or other providers?

Microsoft uses sophisticated filters, including Spam Confidence Level (SCL) and Bulk Complaint Level (BCL), which can be stricter or react differently to certain content/sending patterns than other providers like Gmail. Additionally, Office 365's internal reputation systems might weigh factors unique to its ecosystem.

What are the immediate steps I can take if my Office 365 emails are going to spam?

First, verify your SPF, DKIM, and DMARC records are correctly configured and aligned. Second, monitor your sender reputation using Microsoft's SNDS and Google Postmaster Tools. Third, review your email content for any spam trigger words, excessive imagery, or broken links. Finally, ensure your email list is clean and engage only with active subscribers.

Does a high complaint rate directly affect Office 365 spam filtering?

Yes, high complaint rates from recipients marking your emails as spam significantly damage your sender reputation with Office 365. This tells Microsoft that your emails are unwanted, leading to them being filtered into the junk folder. Implement clear unsubscribe options and send relevant content to reduce complaints.

Can sending too many emails at once cause them to go to Office 365 spam?

Yes, sending emails from a new IP address or domain without gradually increasing your sending volume can trigger spam filters. This practice, known as IP or domain warming, helps build a positive sending history and reputation with mailbox providers, including Office 365.

How can I check my sender reputation with Office 365?

Monitoring your domain and IP reputation through Microsoft's SNDS and Google Postmaster Tools provides direct insights into how these major providers view your sending practices. These tools can show you spam rates, IP reputation, and authentication failures, helping you pinpoint the exact issues.

Why are my emails landing in Office 365 spam folders? - Troubleshooting - Email deliverability - Knowledge base

Emails landing in spam folders, particularly within

Office 365, can be a frustrating experience. It disrupts communication, impacts business operations, and can severely damage your sender reputation. While you might assume your emails are perfectly fine, Microsoft's robust spam filters are constantly evaluating incoming mail. This guide will explore the primary reasons why your legitimate emails might be diverted to the junk folder in Office 365 and what actionable steps you can take to prevent it.

Many factors contribute to this issue, from technical misconfigurations to content that inadvertently triggers spam filters. Unlike other email providers, Office 365 (or Outlook.com) has its own set of sophisticated filters, including Spam Confidence Level (SCL) and Bulk Complaint Level (BCL) scores, which determine whether an email is delivered to the inbox, junk, or quarantine.

Technical authentication failures

A common culprit for emails landing in Office 365 spam is insufficient or incorrect email authentication. SPF, DKIM, and DMARC are crucial for proving that your emails are legitimate and sent from an authorized source.

SPF (Sender Policy Framework): This record specifies which mail servers are authorized to send email on behalf of your domain. If your SPF record is missing, incorrectly configured, or exceeds the 10-lookup limit, Office 365 may flag your emails as suspicious. A hard-fail (minus -all) can lead to emails being spammed by Gmail and Office 365. For more information, read our guide on what SPF means in email.
DKIM (DomainKeys Identified Mail): This adds a digital signature to your emails, allowing the receiving server to verify that the email has not been tampered with during transit and genuinely originated from your domain. A DKIM TempError indicates temporary issues during validation.
DMARC (Domain-based Message Authentication, Reporting, and Conformance): This builds on SPF and DKIM, providing instructions to receiving servers on how to handle emails that fail authentication. A robust DMARC policy (e.g., p=reject) signals to Office 365 that you take email security seriously, improving your chances of inbox delivery. Implement a DMARC p=none policy to start monitoring.

Missing or misconfigured authentication records are one of the most common reasons why emails from your Office 365 tenant or via a third-party ESP end up in spam. Email authentication is fundamental to building sender trust.

Example SPF Record

Basic SPF record for Office 365DNS

v=spf1 include:spf.protection.outlook.com -all

This example allows

Outlook (via spf.protection.outlook.com) to send emails on your domain's behalf and sets a hard fail (-all) for all other sources. Ensure all your legitimate sending services are included.

Sender reputation and blocklists

Microsoft, like other email providers, relies heavily on your sender reputation. This reputation is a cumulative score based on your sending history, complaint rates, bounce rates, and whether your IP or domain appears on any blocklists (or blacklists). A low reputation signals to Office 365 that your emails might be unwanted, leading to them being filtered into spam or even quarantined. This is a common reason why emails are filtered by Microsoft.

High complaint rates occur when recipients mark your emails as spam. This is a strong negative signal, indicating that your content is not desired. Similarly, high bounce rates suggest you're sending to invalid or inactive addresses, which can lead to your domain or IP being put on a blocklist. You should monitor your blocklist status regularly.

Maintaining a clean email list and sending only to engaged subscribers are critical for a healthy sender reputation. If you're sending to an outdated or unverified list, you risk hitting spam traps, which are designed to catch spammers and will immediately damage your reputation. This could be why your transactional emails go to spam, too.

Reputation Factors

To gauge your sender reputation, you should use

Microsoft'sSmart Network Data Services (SNDS) and

GooglePostmaster Tools. These provide valuable insights into your domain's health and any potential issues that Office 365 or Gmail might be seeing.

Content and formatting issues

Even with perfect technical setup and a stellar reputation, your email content can trigger Office 365 spam filters. These filters analyze every element of your message, from subject lines to embedded links and images.

Spammy keywords: Phrases like free money, guaranteed income, or excessive use of exclamation points and all caps can flag your email. This applies to both the subject line and the body.
Image-to-text ratio: Emails that are almost entirely images with little text can be seen as suspicious, as spammers often use images to bypass text-based filters.
Broken links or suspicious URLs: Ensure all links are valid and lead to reputable domains. Using shortened URLs can also sometimes trigger filters.
Poor HTML formatting: Overly complex, sloppy, or non-standard HTML can raise red flags. Keep your email code clean and simple.

Content-based junk filters, often based on heuristics, can be particularly challenging to troubleshoot. If your emails are consistently missing the inbox due to content, you need to re-evaluate your messaging and design choices. For more on this, check out our guide on why emails sometimes end up in the spam folder.

Common Content Triggers

Excessive capitalization: USING ALL CAPS IN SUBJECT LINES OR BODY TEXT.
Too many images: Emails with a high image-to-text ratio, often used by spammers.
Suspect phrasing: Words or phrases commonly associated with phishing or scams.

Best Practices for Content

Balanced content: Aim for a healthy text-to-image ratio.
Clear, concise language: Avoid spam trigger words and excessive punctuation.
Reputable links: Use full, recognizable URLs and ensure they are active.

Engagement and sending volume

Office 365, like most major email providers, monitors engagement metrics closely. If your emails consistently receive low open rates, high unsubscribe rates, or numerous spam complaints, it signals to Microsoft that your recipients aren't interested in your content. This directly impacts your domain's reputation and can lead to future emails being filtered.

Furthermore, a sudden surge in email volume from a new or previously low-volume sender can trigger spam filters. This is often interpreted as a spamming attempt. Gradual warming of new IPs or domains is essential to build a positive sending history with mailbox providers like Office 365. This is critical if you are sending recruitment emails or other types of bulk messages.

Even if your initial emails pass authentication, continuous poor engagement or sudden volume spikes will erode trust over time. You should consistently monitor your engagement data to identify potential issues before they severely impact your deliverability. If you send email newsletters, this is particularly important for ensuring they land in the inbox.

Views from the trenches

Best practices

Always use double opt-in for new subscribers to ensure they genuinely want your emails.

Segment your audience and tailor content to increase engagement and reduce complaints.

Implement clear unsubscribe options in every email to allow disinterested recipients to opt out gracefully, rather than marking as spam.

Monitor your domain and IP reputation using tools like Microsoft's SNDS and Google Postmaster Tools for early warning signs.

Regularly clean your email list by removing inactive or bouncing addresses.

Common pitfalls

Sending emails to purchased or old lists, which often contain spam traps or inactive users.

Ignoring authentication failures (SPF, DKIM, DMARC) or not setting up a DMARC policy.

Sending sudden, large volumes of email without proper IP or domain warming.

Using generic or overly promotional subject lines and content that triggers spam filters.

Not responding to recipient feedback or support requests about emails landing in junk.

Expert tips

Always check SPF, DKIM, and DMARC alignment. Misconfigurations are a primary cause of Office 365 filtering.

Focus on building a strong sender reputation through consistent, high-quality engagement and list hygiene.

Utilize Postmaster Tools and SNDS to gain visibility into how Microsoft views your sending practices.

Review your email content for spammy keywords, disproportionate image-to-text ratios, or broken links.

Gradually increase sending volume, especially from new IPs or domains, to warm up your sending infrastructure.

Marketer view

A marketer from Email Geeks says they started seeing emails land in spam when they initially set up Office 365, despite having simple subject lines. They mentioned this was not an issue with other providers like Gmail or Apple Mail.

2020-02-27 - Email Geeks

Expert view

An expert from Email Geeks says to check your bounce and complaint rates first, as these are strong indicators of issues with Microsoft or other providers. They emphasized that more data is needed to make accurate assumptions.

2020-02-27 - Email Geeks

Achieving inbox placement

Dealing with emails landing in Office 365 spam folders requires a comprehensive approach. It's rarely a single issue but rather a combination of factors related to your authentication, sender reputation, and email content. By methodically addressing each of these areas, you can significantly improve your deliverability and ensure your messages reach the intended inboxes.

Regular monitoring of your email performance metrics, including bounce rates, complaint rates, and inbox placement, is crucial. Tools like Microsoft's dashboard for sender score and DMARC monitoring solutions can provide the insights you need to diagnose and fix issues proactively. Remember, consistent effort in maintaining good sending practices will yield the best long-term results.