How to resolve Office 365 SCL rating issues for corporate email from Google Workspace?
Michael Ko
Co-founder & CEO, Suped
Published 10 May 2025
Updated 17 Aug 2025
7 min read
Dealing with Office 365 Spam Confidence Level (SCL) rating issues for corporate emails originating from Google Workspace can be incredibly frustrating. It's a scenario I've seen play out many times, where perfectly legitimate emails suddenly start landing in spam folders, disrupting critical business communications. This often happens without any obvious changes in sending behavior, leaving IT teams and email marketers scratching their heads.
The challenge is compounded by the interplay between two major email ecosystems: Google Workspace and Microsoft 365. When your corporate emails, which are vital for daily operations, suddenly receive a high SCL, it can feel like you're caught in the middle. I'll walk you through understanding these ratings, identifying potential causes, and actionable steps to resolve these complex deliverability challenges.
Deciphering Office 365 SCL ratings
The Spam Confidence Level (SCL) is a rating assigned by Microsoft's Exchange Online Protection (EOP) to incoming emails, indicating the likelihood of them being spam. A higher SCL value, such as an SCL of 9, means EOP is highly confident the email is spam and will likely route it to the junk folder or even block it. Understanding these scores is the first step in troubleshooting, as they are a direct indicator of how Microsoft perceives your email. You can learn more about SCL in cloud organizations directly from Microsoft's documentation.
It can be perplexing when corporate emails, which are typically low-volume and high-value, suddenly face a sharp increase in their SCL. I often see this when there's no obvious cold emailing or unauthenticated sending. Sometimes, it feels like the domain or IP reputation has been unfairly caught in a wider net, or there's a disconnect in how Google Workspace is being perceived by Microsoft 365, even if your configurations seem correct.
It's important to remember that trying to find a specialcontact or bat phone at Microsoft to bypass standard procedures often isn't effective. Both Microsoft and Google rely on data-driven decisions for deliverability. While it's tempting to seek a shortcut, a structured, data-led approach to identifying and addressing the root causes is the most reliable path to resolving SCL issues and improving your SCL on Outlook.
Foundational email authentication and setup
The cornerstone of good email deliverability, especially between different providers, is robust email authentication. For Google Workspace emails, this means ensuring your SPF, DKIM, and DMARC records are impeccably configured. These protocols act as a digital signature, proving that your emails are legitimate and haven't been tampered with. Without proper authentication, even corporate emails can be flagged, leading to elevated SCL scores. A simple guide to DMARC, SPF, and DKIM can provide a solid foundation.
Common authentication pitfalls
Imperfect DMARC alignment: Even if DMARC is set up, a lack of alignment (strict vs. relaxed) can cause issues. Ensure your DMARC policy aligns properly for all sending sources.
Missing DKIM selectors: Ensure all valid DKIM selectors for Google Workspace are published and correctly configured in your DNS.
SPF record limitations: SPF records have a 10-lookup limit. If you're using many third-party senders, this can lead to SPF TempErrors with Microsoft. Ensure your SPF is authorized and optimized.
Subdomain segmentation is another critical strategy. If your marketing emails are sent from the same domain as your corporate communications, and they incur spam complaints, it can negatively impact your overall domain reputation, leading to higher SCLs for all emails from that domain. Using distinct subdomains for different sending purposes helps isolate reputation issues. For instance, you might use mail.yourdomain.com for corporate and marketing.yourdomain.com for marketing. This is particularly relevant when considering how subdomains affect root domain reputation.
Sender reputation and content considerations
Beyond technical authentication, your sender reputation and email content play significant roles in SCL assignments. Even if your corporate emails are clean, a low overall domain or IP reputation due to other sending activities can be detrimental. Regularly checking your Google Postmaster Tools (GPT) dashboards for spam rates, IP, and domain reputation is crucial. A high spam rate on the marketing side, for example, could be causing collateral damage to your corporate email's SCL.
Content analysis is another key area. Even for corporate emails, certain characteristics can trigger spam filters and increase SCL scores. This includes overly promotional language, broken links, or suspicious attachments. Reviewing your email content for anything that might appear unusual or spammy, even subtly, can help. Here's a quick overview of content factors:
Content factor
Impact on SCL
Spammy keywords
Words like 'free,' 'guarantee,' or excessive capitalization.
Poor formatting
Large images with little text, tiny fonts, or excessive colors.
Suspicious links/attachments
Links to untrustworthy domains or unexepected attachment types.
Ultimately, user engagement, or lack thereof, significantly influences your SCL. High spam complaint rates, even if from marketing emails on a subdomain, can cascade. Encourage recipients to whitelist your emails, and proactively manage opt-ins and opt-outs. If your emails are consistently marked as spam, it tells Microsoft that your mail is unwanted. Monitoring your domain's blacklist status is also a good practice, as being on a blocklist can immediately spike your SCL.
Advanced troubleshooting and engagement with Microsoft
When sudden SCL spikes occur, I've found it's always worth investigating if any email accounts have been compromised. A compromised account can quickly send out large volumes of spam, destroying your sender reputation and impacting your SCL score. Check your Google Workspace logs for unusual sending patterns or suspicious logins. Even if your team is careful, a single compromised account can cause widespread deliverability issues.
Engaging with Microsoft directly can be challenging. While their Microsoft Sender Support portal is primarily for IP blocklist (or blacklist) removals, it often serves as the only formal entry point for SCL-related support. You'll need to clearly articulate that your issue is spam folder placement due to high SCL, not an outright block, and provide message headers for their analysis. This process can be slow and requires patience.
General troubleshooting
Focus on data: Analyze email logs, DMARC reports, and Google Postmaster Tool data to identify patterns or anomalies in your sending.
Review content: Even minor changes in corporate email content can sometimes trigger filters. Look for anything that might be misinterpreted as spam.
Check for abuse: Confirm no accounts are compromised or sending unauthorized mail.
Microsoft engagement for SCL issues
Formal support: Microsoft's corporate support generally requires a support contract. Consider if your organization has one, or if a recipient with a high-level contract can open a ticket.
Sender support portal: Use the Microsoft Sender Support portal, even though it's geared towards blocking, as it is the official channel.
Provide comprehensive details: Include full message headers, specific examples of emails sent to spam, and detailed explanations of your email practices.
It's important to understand that Microsoft's support model for corporate products often relies on paid support contracts or the partner ecosystem. Free support is usually limited to forums. This means that for complex SCL issues not related to an outright IP block, you may need to leverage existing relationships with Microsoft partners or ensure your organization has a robust support agreement in place to get the deeper assistance needed. This approach is often more effective than repeated inquiries through generic channels, helping you fix Outlook junk mail placement.
Views from the trenches
Best practices
Maintain separate subdomains for different email streams, such as marketing vs. transactional emails.
Regularly review your DMARC reports to spot authentication failures or anomalies.
Continuously monitor your domain and IP reputation using tools like Google Postmaster Tools.
Keep your email content clean and professional, avoiding elements commonly associated with spam.
Common pitfalls
Failing to implement or correctly configure all email authentication protocols (SPF, DKIM, DMARC).
Ignoring spam complaint rates, especially for marketing emails, which can affect corporate sender reputation.
Not segmenting email sending by subdomain, allowing one stream to damage the reputation of another.
Expecting immediate resolution from Microsoft without providing detailed data or having a support contract.
Expert tips
Use a structured, data-driven approach to investigate and resolve SCL issues, as there are no magic shortcuts.
Consider a formal Microsoft support contract or working through a Microsoft Gold partner for complex deliverability challenges.
Understand that Microsoft's official sender support portal is the primary channel, even for SCL-related filtering issues, not just IP blocklists.
If using Google Workspace, continuously align with their best practices to ensure optimal outbound deliverability.
Expert view
Expert from Email Geeks says to check email authentication and ensure the client is not engaging in cold lead emailing, as these are often overlooked causes.
Oct 16, 2024 - Email Geeks
Expert view
Expert from Email Geeks says that sometimes high SCLs can be due to a conflict between major providers like Google and Microsoft, or if the client is new to Google Workspace, it might resolve itself over several weeks.
Oct 16, 2024 - Email Geeks
Navigating your path to inbox success
Resolving Office 365 SCL rating issues for emails from Google Workspace requires a multi-faceted approach. It's rarely one single factor but rather a combination of technical configurations, sender reputation, and content quality. Focusing on robust email authentication, smart subdomain strategy, and diligent monitoring of your domain's health are paramount. This holistic strategy is key to avoiding common pitfalls and ensuring your emails reach their intended inboxes.
The path to resolution may not be instantaneous, and direct intervention from Microsoft can be limited without proper support channels. However, by adhering to best practices and systematically troubleshooting the potential causes, you can significantly improve your email deliverability and maintain a strong sender reputation across all platforms. This ensures your critical corporate communications are always delivered reliably.
Microsoft's Exchange Online Protection (EOP) to incoming emails, indicating the likelihood of them being spam. A higher SCL value, such as an SCL of 9, means EOP is highly confident the email is spam and will likely route it to the junk folder or even block it. Understanding these scores is the first step in troubleshooting, as they are a direct indicator of how Microsoft perceives your email. You can learn more about SCL in cloud organizations directly from Microsoft's documentation.
Google Workspace is being perceived by Microsoft 365, even if your configurations seem correct.
