How to Reduce Infomail Spam in Microsoft Office 365
If your users are complaining about inboxes full of newsletters, marketing emails, and automated notifications, you’re not alone. Many organizations using Microsoft 365 struggle with what people often call “infomail” — messages that aren’t technically spam but still clutter inboxes.
These emails usually come from legitimate platforms like marketing automation tools or mailing lists. Because they are authenticated and compliant with email standards, Microsoft 365 doesn’t always classify them as spam by default.
Fortunately, there are several ways administrators can reduce this type of email dramatically.
In this guide, we’ll walk through the most effective methods to reduce infomail spam in Microsoft 365.
Why Infomail Gets Through Microsoft 365 Spam Filtering
In Microsoft 365, email filtering separates messages into categories such as:
- Malware
- Phishing
- Spam
- Bulk email
Most newsletters and promotional campaigns fall into the bulk email category. These messages are scored using Microsoft’s Bulk Complaint Level (BCL) rating system, which ranges from 0 to 9.
Higher BCL scores indicate a higher likelihood that recipients consider the message unwanted.
By default, Microsoft 365 allows many bulk messages through because they are technically legitimate marketing emails.
That’s why adjusting bulk email filtering is the most effective way to reduce infomail.
Step 1: Increase the Bulk Email Filtering Threshold
The fastest way to reduce newsletters and marketing emails is to adjust the Bulk Complaint Level threshold.
How to change the bulk email threshold
- Sign in to the Microsoft 365 Defender portal
- Go to Email & Collaboration → Policies & Rules → Threat Policies
- Open Anti-spam policies
- Edit the Anti-Spam inbound policy (or create a custom policy)
- Locate Bulk email threshold
Recommended settings
| BCL Threshold | Filtering Level | Result |
|---|---|---|
| 7 (default) | Standard | Most newsletters allowed |
| 6 | Moderate | Many marketing emails filtered |
| 3 | Aggressive | Most infomail blocked |
Most organizations that want to reduce infomail significantly set this value between 3 to 6.
You can then choose the action for bulk messages:
- Move to Junk
- Send to Quarantine
- Tag with a warning header
Sending bulk mail to Quarantine is often the best choice because users can still retrieve legitimate emails if needed.
Step 2: Enable Preset Security Policies
Another quick way to strengthen email filtering is to enable stricter preset security policies.
Microsoft provides two recommended options:
- Standard Protection
- Strict Protection
Strict protection applies stronger filtering rules for:
- spam
- bulk mail
- phishing attempts
- spoofed domains
Many organizations apply Strict protection to executives or high-risk users, while applying Standard protection organization-wide.
Step 3: Use Advanced Spam Filter (ASF) Settings
Microsoft 365 also includes Advanced Spam Filtering (ASF) rules that can help catch additional unwanted mail.
These rules can increase spam confidence when emails contain characteristics such as:
- suspicious HTML structures
- certain link types
- spoofing indicators
- unusual sending patterns
Because ASF settings can increase false positives, administrators should enable them selectively and monitor quarantine results.
Final Thoughts
Infomail is one of the most common frustrations for organizations using Microsoft 365. Because these messages often come from legitimate senders, they frequently bypass traditional spam filters.
By adjusting bulk email filtering settings, enabling stronger policies, and encouraging responsible mailing list management, administrators can significantly reduce inbox clutter.
A few simple changes in Microsoft 365 can often reduce infomail by 50–80 percent, improving productivity and user satisfaction across the organization.
