Legitimate vs. Spam Messages: Breaking Down Microsoft’s Rating System. Every email marketer wants to know the secret to landing messages in the inbox, but most know how complex and tricky it can be to achieve.

• Microsoft applies three hidden scores to every email — SCL, BCL, and PCL — and these directly determine whether your message lands in the inbox or goes to Junk.
• SCL (Spam Confidence Level) measures how "spammy" your message looks based on content and patterns.
• BCL (Bulk Complaint Level) reflects how likely your audience is to complain about your messages.
• PCL (Phishing Confidence Level) evaluates whether your content resembles phishing attempts.
• High scores in any of these categories can cause instant Junk folder placement across Outlook/Hotmail.
• Pulling these values from your headers is one of the most reliable ways to diagnose Microsoft deliverability issues.

• What exactly is Microsoft scanning when my email hits their servers?Microsoft’s Exchange Online Protection (EOP) immediately analyzes the message and inserts an anti-spam report into your headers.The most important fields are:SCL → How spam-like the message appears
• BCL → How likely recipients are to complain
• PCL → How suspicious or phishy the content seems

These values heavily influence inbox placement.

• How does the SCL score affect inboxing?SCL is Microsoft’s internal "spam scorecard":–1 → Safe sender, guaranteed inbox
• 0–1 → Clean content, inbox
• 5–9 → Increasingly spammy → goes to Junk

Scores 2, 3, 4, 7, 8 aren’t used at all — you’ll only see the ones above.

• What does the BCL score mean for my reputation?BCL measures historical complaint patterns:0 → Not considered a bulk sender
• 1–3 → Low complaint risk
• 4–7 → Mixed complaint behavior
• 8–9 → High complaints → strong Junk folder risk

If your BCL trends high, your audience is signaling negative engagement.

How does the PCL score relate to phishing?PCL scores 0–3 indicate non-suspicious content, while scores 4–8 suggest potentially phishing material that triggers Microsoft warnings and filtering.

Every email marketer would love to know the special sauce that gets their messages directly into the intended recipient’s inbox. However, most marketers, especially those who’ve been doing it for a while, know just how complicated and tricky that task can be.

ISPs give us a few of their secret ingredients here and there, but most scanning and filtering tools that ISPs use are not shared publicly — and for good reason! No one wants spam in their inbox! And if spammers knew all the secrets, they could circumvent them. But for legitimate senders who need to get an email to people who have asked for their messages, sometimes it can be frustrating.

One of the clues Microsoft gives us into how they measure the legitimacy of your email message lies in the headers. In the last few years, they’ve introduced a rating system that determines how spammy or phishy they believe a message to be as well as how likely the sender is to generate spam complaints.

As soon as an email message hits Microsoft’s servers, their proprietary Exchange Online Protection (EOP) filtering service scans the message and then inserts an anti-spam report into the message headers. You can read more about all of the different fields and filters they use here, but the three fields that I’m going to focus on today that have helped us understand how messages are being processed are:

SCL = The Spam Confidence Level

PCL = The Phishing Confidence Level

BCL = The Bulk Complaint Level

When opening the message headers you can do a search for X-Forefront-Antispam-Report and find the SCL ratings underneath. BCL and PCL ratings can be found under the X-Microsoft-Antispam section. Here’s a screenshot of the message headers from a message I received in my Outlook account where I’ve highlighted these ratings.

SCL — Spam Confidence Level

After the email is received and goes through the EOP spam filtering it’s given an SCL score. Here’s a breakdown of what each means:

Rating

Meaning

Inbox/Junk Behavior

-1

Trusted safe sender

Delivered to inbox

0–1

Not spam

Delivered to inbox

5–9

Increasing confidence of spam

Sent to Junk folder

2, 3, 4, 7, 8

Not assigned

N/A

-1 = A special value that means the message is a safe sender and is not spam. This score tells Microsoft to put the message in the inbox. 0-1 = The content of the message was scanned and determined to not be spam. These two scores also tell Microsoft to deliver the message to the inbox. 5-9 = Starting with a score of 5 the message is suspected to be spam and is increasingly likely to be sent to the Junk folder.

So what can we take away from these ratings? If you’re having junk foldering issues at any of the Microsoft domains check your SCL, BCL, or PCL ratings. If any of these are high, it could be the cause of the junk foldering. Microsoft doesn’t disclose the specific criteria for how they assign these ratings, but looking at the ratings will let you know what aspect of your email sending you may need to improve to get better inbox placement, be it the message content or your sending practices.

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