Trying to deliver emails to Outlook?

If you just answered “Yes”, you are not alone. Outlook inboxes can be a tricky destination to reach.

Microsoft’s Outlook email platform uses advanced filtering technology to identify and block unwanted messages, which can be a barrier for legitimate emails that don’t fully align with their criteria. To improve deliverability to Outlook inboxes, it’s crucial to understand how Microsoft’s filtering system works and what specific steps can help you land in the inbox rather than the spam folder.

Let’s take a closer look at how Microsoft’s SmartScreen filtering works and how you can optimize your emails to navigate these filters successfully.

Understanding Microsoft’s Filtering System

Outlook's filtering relies on SmartScreen, which has been designed to detect spam, phishing, and other unwanted messages. Here are some of the main factors it considers:

• Sender Reputation: Microsoft tracks the history of IP addresses, domains, and individual email accounts. A positive sender reputation is built over time through consistent engagement (opens, clicks, replies) and low complaint rates. If your emails generate frequent complaints or low engagement, your reputation may decline, making future emails more likely to be flagged.

• Recipient Engagement: Outlook evaluates how recipients interact with your emails. High engagement, such as frequent opens or replies, boosts your reputation.

• Email Content and Formatting: SmartScreen examines the structure and content of emails, looking for red flags that might indicate spam. This includes evaluating subject lines, body text, the balance of images and text, and the presence of links or attachments.

• Spam Triggers and Blacklists: Microsoft also uses additional signals, such as third-party spam filters and public blacklists, to detect and block potential spam emails. If your IP or domain has been reported or blacklisted, this will negatively impact your deliverability.

Spam Confidence Level (SCL) Score

Microsoft assigns every inbound email a Spam Confidence Level (SCL) score, a key component of its filtering system. The SCL score is essentially a rating that indicates the likelihood of an email being spam, and it ranges from 0 to 9. Lower scores (closer to 0) indicate that an email is considered safe, while higher scores (closer to 9) signal a high likelihood of spam. Based on this score, Outlook may deliver the email to the inbox, direct it to the junk folder, or block it entirely.

Strategies to Improve Deliverability to Outlook Inboxes

With this knowledge in mind, let’s look at actionable ways to enhance your deliverability to Outlook mailboxes.

Craft High-Quality, Engaging Content

Creating valuable, well-written content is essential. Avoid “spammy” language like “FREE!!!” or “LIMITED TIME OFFER.” Make your subject lines clear and specific, and keep the body text relevant and engaging. By focusing on content that resonates with your audience, you’ll naturally increase engagement, which is a major plus in Microsoft’s filtering criteria.

Control Your Email Volume

Outlook is sensitive to high-volume sending, especially from newer or unproven senders. Sending too many emails at once can make Microsoft’s filters see you as a potential spammer. If you’re scaling up your email efforts, start small and gradually increase your volume. This helps you build a solid reputation over time rather than overwhelming the system.

Reach Out to Microsoft Support for Ongoing Issues

If you’re consistently facing deliverability issues, Microsoft Support may be able to assist. They can guide you on sender reputation concerns or other filtering aspects that may impact your deliverability.

Regularly Test Your Deliverability

Email deliverability tools can be extremely valuable for assessing your emails' performance across providers, including Outlook. These tests reveal if your emails are landing in the inbox, spam folder, or being blocked entirely, allowing you to make data-driven adjustments.

Rotate Multiple IP Addresses for High Volume

If you send large volumes of email, consider rotating between multiple IP addresses. This practice can help distribute your email traffic more evenly, preventing any single IP from accumulating too much activity and triggering spam filters. Ensure each IP address has a positive reputation before adding it to your rotation.

Use Dedicated Email Infrastructure

If possible, avoid using shared IPs or domains for email campaigns. A dedicated IP and domain allow you to build and maintain your own reputation, isolated from other senders who may have poor practices. This is particularly valuable if you send large volumes of email and need consistent deliverability.

Conduct Regular DNS and IP Health Checks

IP reputation and DNS settings are critical to your deliverability. If your IP is blacklisted or your domain’s DNS settings are misconfigured, Outlook’s filters are more likely to view your emails as suspicious. Use tools to regularly check your IP’s status and verify that your DNS, SPF, and DKIM settings are correct and up to date.

Simplify with Plain Text Emails

Plain text emails typically have a better chance of making it to the inbox in Outlook. HTML-heavy emails can often be flagged by Microsoft’s filters, especially if they contain too many images or unnecessary styling. Stick with plain text or minimal HTML for a higher likelihood of bypassing the spam filter.