How can I improve my Spam Complaint Level (SCL) on Outlook?
Updated on 29 Sep 2026: We updated this guide for Microsoft's current cloud filtering model, including CAT-based diagnosis, BCL handling, and Outlook Promotions routing.
Microsoft uses SCL to mean Spam Confidence Level, not Spam Complaint Level. In Microsoft 365 cloud filtering, SCL is stamped in a message header but no longer determines whether Microsoft labels the message as spam or high-confidence spam, or which action follows. Microsoft's SCL documentation says to read message categorization and related header evidence instead. Complaints still matter because unwanted mail, stale consent, weak engagement, and bulk sending patterns affect reputation and placement.
If a confirmed opt-in message reaches the inbox with SCL 1 while later marketing mail reaches junk with SCL 5, the difference between the streams is still useful. The numbers alone do not explain the routing. Compare CAT, SFV, DIR, BCL, authentication results, URLs, recipient activity, and send patterns before choosing a fix.
Fast answer
- Consent: send marketing only to people who clearly asked for it, not people who missed a pre-checked box.
- Complaints: suppress every known complainer, including feedback loop and junk mail reporting data.
- Engagement: send first to recent buyers, clickers, and subscribers who still show intent.
- Headers: diagnose CAT, SFV, DIR, and BCL instead of treating SCL as the final cloud verdict.
- Infrastructure: check SPF, DKIM, DMARC, link domains, redirects, and blocklist (blacklist) status.
What SCL means in Outlook
SCL is a value in the X-Forefront-Antispam-Report header. Historically, a higher value indicated that spam filtering considered a message more likely to be spam. In Microsoft 365 cloud organizations, SCL no longer determines the Spam or High confidence spam category and no longer determines the delivery action. The same SCL can appear on messages with different verdicts.
SCL remains important for on-premises Exchange content-filter thresholds and hybrid delivery to on-premises mailboxes. In the cloud, its main use is in mail flow rules that request a filtering bypass or ask Microsoft to treat mail as spam. Even a bypass request might be stamped SCL 0 or 1 after evaluation. For cloud troubleshooting, read SCL beside CAT, SFV, DIR, BCL, Authentication-Results, X-CustomSpam when present, and the applied receiving policy. For a header-by-header workflow, compare this with SCL headers.
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SCL | Legacy spam confidence value | X-Forefront-Antispam-Report | Treat as context, not the final cloud verdict |
CAT | Filtering category | X-Forefront-Antispam-Report | Identify what classified the message |
SFV | Spam filtering verdict or override | X-Forefront-Antispam-Report | Trace content filtering, rules, or allow and block decisions |
DIR | Inbound, outbound, or internal direction | X-Forefront-Antispam-Report | Confirm which processing path applied |
BCL | Bulk complaint likelihood | X-Microsoft-Antispam | Compare with the recipient's bulk threshold |
Header fields that explain Microsoft 365 cloud filtering.
When placement looks unexpected, start with CAT and SFV. CAT identifies the category that won, while SFV can reveal spam filtering, a blocked sender, a safe sender, an IP allow entry, or a mail flow rule. DIR confirms whether the message was inbound, outbound, or internal. If X-CustomSpam exists, an Advanced Spam Filter setting also affected the message.
Microsoft Defender for Office 365 message details with SCL 5, BCL 4, and authentication results.
How SCL and BCL differ
SCL and BCL now answer different questions in Microsoft 365 cloud mail. SCL is a historical confidence value that remains in the headers, but it does not control the cloud verdict. BCL, or Bulk Complaint Level, estimates how likely mail from an identified bulk sender is to exhibit unwanted, spam-like behavior. A marketing message can pass SPF, DKIM, and DMARC and still receive a high BCL because authentication proves domain control, not recipient demand.
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SCL | Legacy confidence context | -1, or 0 to 9 | Do not optimize the number by itself |
BCL | Bulk complaint likelihood | 0 to 9 | Improve consent, targeting, and complaint suppression |
CAT and SFV | Category and filtering evidence | Header codes | Identify the detection or override |
How to interpret SCL and BCL in Microsoft 365 cloud mail.
Microsoft categorizes BCL 1 to 3 as bulk mail with few complaints, 4 to 7 as a mixed complaint level, and 8 to 9 as a high complaint level. BCL 0 means the message was not identified as bulk. The default anti-spam policy uses threshold 7, Standard uses 6, and Strict uses 5. A message that meets or exceeds the applicable threshold receives the configured bulk action. Default and Standard policies normally send it to Junk, while Strict normally quarantines it. Recipient administrators can tune a false positive, but that does not repair the sender's underlying consent or reputation problems.
Why confirmed opt-in lands in inbox
A confirmed opt-in email usually has the best possible timing. The recipient just asked for it, expects a specific step, and receives a narrowly focused message. That is why a confirmation email can reach the inbox with SCL 1 while a plain-text marketing message reaches junk with SCL 5. The placement difference matters more than the numerical gap.
Changing HTML to plain text does not fix a trust problem. If Microsoft distrusts the campaign stream, a simpler template will not remove stale subscribers, complaints, weak acquisition sources, reused tracking links, or an aggressive cadence. Make the marketing stream behave more like wanted mail, then verify the resulting category and placement.
Confirmation email
- Timing: sent seconds after the subscriber action.
- Intent: recipient expects a specific confirmation step.
- Scope: narrow content with few links and little promotion.
Marketing email
- Timing: sent later, often at a brand-defined cadence.
- Intent: recipient interest has to be proven again.
- Scope: wider audience, tracking links, offers, and repetition.
Fix list quality before content
The fastest route to better Outlook placement is usually a cleaner Microsoft audience. Split Outlook and Microsoft 365 recipients into their own recovery segment, then send only to people with recent, measurable intent. Use recent clicks, purchases, account activity, or a fresh confirmation, not just old opens.
Feedback loops matter here. FBL means feedback loop. JMR means junk mail reporting. When a recipient reports mail as junk and that data reaches you, suppress that person from marketing immediately. Do not wait for a weekly list-cleaning job or move the address into another promotional stream.
- Active opt-in: keep confirmed opt-in for new subscribers and reconfirm weak acquisition sources.
- Complaint removal: remove every address tied to FBL, JMR, abuse desk, or direct complaint signals.
- Recency filter: restart Outlook sends with subscribers active in the last 30 to 90 days.
- Frequency cap: reduce repeat sends to people who ignore multiple campaigns.
- Offer match: stop promoting products a customer already bought unless the message has clear next-step value.
Practical suppression logic
if complaint_received = true then suppress_marketing if last_click > 180 days and no purchase then pause_marketing if source = unknown then request_reconfirmation if outlook_engagement = none for 90 days then throttle
Check authentication and sending identity
Authentication does not override recipient dislike, but broken authentication can make an Outlook placement problem worse. Check that SPF passes, DKIM passes, and DMARC passes for the visible From domain. Also compare whether confirmation mail and marketing mail use the same return-path domain, DKIM signing domain, tracking domain, sending IP pool, and visible From address.
Current Outlook.com high-volume requirement
A domain that sends at least 5,000 messages to Microsoft consumer email services using the same 5322.From domain must have SPF and DKIM pass, publish DMARC, and pass DMARC through a matching authenticated SPF or DKIM domain. Microsoft can reject noncompliant mail with 550 5.7.515. That rejection is an authentication failure, not an SCL verdict, so fix it before running placement tests.
A quick way to separate infrastructure issues from audience issues is to run a domain health checker pass, then compare authentication results between the confirmation stream and the marketing stream. If both pass cleanly but only marketing reaches junk, keep most of your effort on consent, complaints, and engagement.
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What's your domain score?
Deep-scan SPF, DKIM & DMARC records for email deliverability and security issues.
Suped helps with this workflow by turning DMARC aggregate data into source-level findings, authentication trends, and concrete fix steps. Its DMARC monitoring shows which services send for your domain, which ones pass, and which ones need SPF, DKIM, or DMARC fixes before more Outlook placement tests.
Example DMARC record for monitoringDNS
v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com; adkim=s; aspf=s; pct=100
Audit links, domains, and reputation
Outlook filtering does not only evaluate the sender. It also evaluates what the message points to. A plain-text email can still carry a tracking domain, redirect chain, coupon URL, image host, or landing page path with poor history. If those same URLs appeared in campaigns that recipients did not want, Microsoft can treat new mail with more suspicion.
Review every domain in the message, including the visible brand domain, click-tracking domain, image host, unsubscribe domain, and any short links. Then check IP and domain reputation through blocklist monitoring. A blocklist or blacklist listing does not explain every Microsoft junk placement, but it is a concrete issue to remove before deeper campaign testing.
Link checks that matter
- Tracking domain: keep it branded and avoid sharing it across unrelated senders.
- Redirect path: remove unnecessary hops before the final landing page.
- Unsubscribe link: make it visible, direct, and working without a login.
- Blacklist status: investigate blocklist or blacklist listings before increasing Outlook volume.
Consent, complaints, engagement, authentication, and link reputation signals that affect Outlook SCL.
Test the message the way Outlook sees it
Do not judge a fix from one internal mailbox or one SCL number. Send controlled tests to real Outlook.com and Microsoft 365 recipients, then compare the full headers from the confirmation email, a recent marketing email, and a trimmed recovery send. Use an email tester to inspect authentication, content, visible URLs, and technical issues before sending more volume.
The most useful test is a small Microsoft-only send to a recently engaged segment. If that group gets better placement, the sender can recover. If recent clickers still reach junk, inspect CAT, SFV, DIR, BCL, the sending identity, link chain, X-CustomSpam, and any receiving policy that affects the test mailboxes. For more placement work, see Outlook placement.
Email tester
Send a real email to this address. Suped shows a results button when the test is ready.
?/43tests passed
When reviewing headers, compare specific fields rather than relying on inbox or junk alone. A recovery test should show passing authentication, a consistent sender identity, controlled URLs, and clear category evidence. Track placement by recipient cohort as well, because SCL itself is no longer a reliable cloud success metric.
Header fields to compare
X-Forefront-Antispam-Report: SCL:5; SFV:SPM; CAT:SPM; DIR:INB; SRV:BULK X-Microsoft-Antispam: BCL:4 X-CustomSpam: <present only when an ASF setting triggered> Authentication-Results: spf=pass dkim=pass dmarc=pass Return-Path: bounce.yourdomain.com From: news@yourdomain.com List-Unsubscribe: <mailto:unsubscribe@yourdomain.com> List-Unsubscribe-Post: List-Unsubscribe=One-Click
Microsoft 365 BCL interpretation bands
Compare the message's BCL with the threshold and action in the recipient's applicable anti-spam policy.
Not identified as bulk
0
The message was not identified as coming from a bulk sender.
Few complaints
1, 2, 3
Bulk mail associated with few recipient complaints.
Mixed complaints
4, 5, 6, 7
Bulk mail associated with a mixed complaint level.
High complaints
8, 9
Bulk mail associated with a high complaint level.
Account for Outlook's Promotions folder
Outlook placement can now include a Promotions folder as well as Inbox, Junk, and quarantine. Microsoft applies a Promotions tag to messages identified as bulk, regardless of BCL. When the recipient organization's applicable anti-spam policy enables bulk moves, bulk mail below the BCL threshold can go to Promotions instead of the Inbox in supported Outlook clients.
This routing is separate from SCL. A message can have sound authentication, stay below the bulk threshold, and still reach Promotions because it was identified as bulk. Microsoft also learns when users move messages into or out of that folder, so test reports should record the exact folder rather than treating every non-junk delivery as Inbox placement.
How to read a Promotions result
- Check bulk evidence: inspect SRV and BCL to confirm that Microsoft identified the message as bulk.
- Confirm policy scope: recipient administrators control whether eligible mail moves to Promotions.
- Track folder placement: separate Inbox, Promotions, Junk, and quarantine results in every test.
- Keep improving demand: better consent and targeting reduce unwanted-mail signals even when Promotions routing is enabled.
A practical recovery sequence
Once junk placement is repeatable, stop changing multiple variables at once. A controlled recovery sequence makes the problem measurable. Run it over several sends because Microsoft needs consistent positive signals before filtering and placement improve.
- Pause risk: stop broad Outlook sends to inactive recipients while you diagnose the source.
- Export complaints: remove every address tied to junk reports, abuse replies, and direct spam complaints.
- Segment intent: create a Microsoft-only segment of recent buyers, clickers, and confirmed subscribers.
- Reduce volume: send smaller batches and avoid sudden spikes after a junk placement event.
- Simplify URLs: use the fewest necessary links and remove redirect chains you do not control.
- Compare evidence: track CAT, SFV, DIR, BCL, authentication results, and exact folder placement after each test.
- Scale slowly: add less recent segments only after the engaged Microsoft cohort improves.
Six-step Outlook SCL recovery flow for complaints, segmentation, testing, and controlled scaling.
Where Suped fits
Suped is our DMARC reporting and email authentication platform. It helps teams separate authentication faults from reputation or audience problems by showing each sending source, SPF, DKIM, and DMARC outcomes, plus guided fix steps. Suped does not lower SCL directly or make unwanted marketing wanted. It provides the technical evidence needed to find a failing source before more Outlook tests are sent.
Use Suped to monitor DMARC, alert on new failures, identify sources that are approaching SPF DNS lookup limits, and review blocklist (blacklist) signals beside authentication trends. Agencies and MSPs can keep the same checks organized across client domains.
Issue steps to fix dialog showing the issue overview, tailored fix steps, and verification action
Use Suped for the technical layer
- Issue detection: find failed SPF, DKIM, DMARC, rDNS, and source-level problems faster.
- Action steps: turn authentication failures into plain fix instructions for the right owner.
- Policy staging: use hosted DMARC to move toward stronger protection without blind changes.
- Reputation checks: review blacklist and blocklist signals beside authentication and source data.
Views from the trenches
Best practices
Treat confirmed opt-in as the consent floor, then segment marketing by recent intent signals.
Remove Microsoft complainers and hard bounces quickly, before the next campaign wave sends.
Compare inboxing confirmation mail with marketing mail before changing authentication settings.
Common pitfalls
Assuming plain text fixes placement when the recipient set and link history stay unchanged.
Keeping passive consent records after complaint data proves the audience did not want mail.
Using the same tracked links in wanted and unwanted channels, then blaming template HTML.
Expert tips
Throttle Outlook sends first, then rebuild volume with recipients who clicked within 60 days.
Create a separate test seed path, but judge recovery by real recipient engagement over time.
Review JMR and FBL feeds daily so complaint signals turn into immediate suppression.
Marketer view
Marketer from Email Geeks says active opt-in matters because passive consent creates complaint risk when recipients did not expect marketing mail.
2022-11-18 - Email Geeks
Marketer view
Marketer from Email Geeks says if confirmation mail and marketing mail share the same setup, the marketing audience and offer deserve the first review.
2022-11-18 - Email Geeks
The shortest path to better Outlook placement
The direct fix for Outlook placement is to make the marketing stream more wanted and easier to trust. Suppress complaints, rebuild around active consent, reduce Microsoft volume to engaged recipients, and prove that SPF, DKIM, DMARC, link domains, and blacklist or blocklist status are clean. Use CAT, SFV, DIR, and BCL to explain what happened in cloud filtering.
When a confirmation email reaches the inbox and marketing reaches Junk or Promotions, do not spend weeks polishing template details before checking list quality. The confirmation email shows Microsoft can accept your mail. The campaign result shows that the broader stream has different audience, bulk, or reputation signals. Treat SCL as supporting context, not the target metric.
