Kesslernity · M365 Copilot Field Guide
Prioritize My Inbox
Rank before you open.
Copilot reviews every incoming email in real time and assigns High, Normal, or Low priority — based on sender, job title, email content, and up to 15 rules you write in plain English. When you open a flagged email, the reading pane explains exactly why it was ranked.
Status Generally Available
Updated April 2026
Licence Paid Copilot add-on required
Works in New Outlook for Windows · Outlook on the web
Published by kesslernity.com
Licence required before you start

Prioritize My Inbox requires the Microsoft 365 Copilot paid add-on. It is not available on base M365 plans (Business Basic, Business Standard, E3, E5 without the Copilot add-on). If you cannot find Settings → Copilot → Prioritize in Outlook, your Copilot licence may not be assigned — check under Settings → Subscriptions or contact your Microsoft admin. Included in M365 E7 (generally available May 1, 2026). There is no admin kill switch — users opt in individually.

At a glance
What Copilot reads
Incoming emails in real time — sender identity,
job title, email body, and your custom rules.
What it cannot prioritise
Emails already in your inbox before you enabled
the feature. Forward-looking only, not retroactive.
The highest-return part
The reasoning pane — opens when you click a
flagged email and shows exactly why it was ranked.
ComponentWhat it doesWhere it appears
Priority rankingAssigns High, Normal, or Low to every incoming email automatically on arrivalBackground — no action needed
Up arrow indicatorMarks High priority emails visually in the message listNext to sender name in inbox
Reasoning paneExplains which rule or signal triggered the priority call for each emailReading pane when email is open
Custom rules (15 max)Plain-English instructions for what to surface and what to suppress — shared across High and LowSettings → Copilot → Prioritize
Down arrow (optional)Marks Low priority emails — newsletters, notifications, CC-only threadsEnable separately in Prioritize settings
Prioritize My Inbox vs Focused Inbox vs Copilot Chat
Tool How it decides Configurable? Licence
Prioritize My Inbox AI reads content, sender title, and your custom plain-English rules. Shows reasoning per email. Yes — up to 15 rules in plain English Paid Copilot add-on
Focused Inbox Microsoft's algorithm segments emails into Focused and Other tabs based on engagement history. No rule input. No — learns from behaviour only Included in base M365
Copilot Chat (inbox) Queries your inbox on demand — "What emails need my reply today?" — but does not passively rank on arrival. Via prompts at query time Paid Copilot add-on
Manual Outlook rules Pattern-matching on sender, subject, and keywords — moves, flags, and categorises by explicit conditions. Yes — but requires exact syntax, no natural language Included in base M365
Setup — 4 steps
1
Open Prioritize settings
In new Outlook for Windows or Outlook on the web: Settings → Copilot → Prioritize. This path does not exist in the classic Outlook desktop client. If it is missing, confirm you are using the new Outlook version.
2
Write your first High priority rule
Type a plain-English instruction in the High priority box — for example, Emails from my manager or direct reports. Add one rule at a time. Rules take approximately 15 minutes to activate.
3
Add Low priority rules to suppress noise
In the Low priority box, suppress predictable noise: Newsletters, automated notifications, and emails where I am only CC'd. High and Low priority rules share the 15-rule total.
4
Calibrate using the reasoning pane
For the first week, open flagged emails and read the reasoning pane. It shows exactly which rule fired. Adjust any rule that flags inconsistently. Disabling a rule takes up to 24 hours to take effect.
The 15-rule system — rules by role
High and Low priority share the same 15-rule budget
Rule sets by role — what to add for High and Low priority
Project Manager
PM · Delivery Lead · Programme Manager
Most common starting point
High priority — add these rules
  • Emails from my project sponsor or client
  • Emails mentioning a milestone date, change request, or budget approval
  • Emails where someone is blocked and waiting on my response
  • Emails from the steering committee or governance board
Low priority — suppress this noise
  • Automated project system notifications where no action is required
  • Emails where I am only CC'd and not the primary addressee
  • Distribution list updates and system-generated reports
Sender-based rules (project sponsor, client name) are the most reliable from day one. Content-based rules (milestone, change request) improve over the first week as Copilot learns your project vocabulary.
Finance and Accounting
Finance Manager · Controller · FP&A Analyst
High-volume, deadline-driven
High priority — add these rules
  • Emails about month-end close, variance reports, or audit requests
  • Emails from the CFO, controller, or finance leadership
  • Emails with payment approval requests or invoice escalations
  • Emails mentioning a budget deadline or financial submission date
Low priority — suppress this noise
  • Automated reports I receive for information only
  • Bank notification emails and system-generated confirmations
  • Finance industry newsletters and regulatory update digests
Month-end periods will generate more High priority flags — this is expected. Consider temporarily adjusting your rules during close weeks if volume becomes disruptive.
Legal, Compliance, and Risk
Legal Counsel · Compliance Officer · Risk Manager · HSE Lead
High-stakes, cannot miss
High priority — add these rules
  • Emails containing contract review deadlines or regulatory filing dates
  • Emails from external counsel or the compliance team
  • Emails referencing litigation, regulatory response, or breach notification
  • Emails about audit findings requiring a written response
Low priority — suppress this noise
  • Legal industry newsletters and bar association updates
  • Automated system alerts received for logging purposes only
For roles where missing an email has compliance implications, use Prioritize My Inbox alongside — not instead of — your existing flagging and folder discipline.
Executive Assistant and Chief of Staff
Executive Assistant · PA · Chief of Staff · Office Manager
Inbox management at scale
High priority — add these rules
  • Emails from the executives I support
  • Emails with meeting requests requiring same-day scheduling action
  • Emails marked urgent by a C-suite member or board contact
  • Emails about travel changes, visa requirements, or logistics for upcoming trips
Low priority — suppress this noise
  • Automated calendar notifications and meeting room confirmations
  • Distribution list emails that do not require action from me
  • Vendor marketing and product update emails
EAs managing multiple executives may hit the 15-rule ceiling quickly. Prioritise rules for the executive with the highest-consequence schedule first, then add others as budget allows.
Procurement and Supply Chain
Procurement Manager · Buyer · Supply Chain Lead · Expeditor
Delay-sensitive, vendor-heavy
High priority — add these rules
  • Emails about supplier delays, delivery confirmations, or PO approvals
  • Emails from vendors on active contracts where delivery is within 30 days
  • Emails about expediting requests or logistics escalations
Low priority — suppress this noise
  • Vendor catalogue updates and promotional emails
  • Automated PO acknowledgement confirmations
  • Internal newsletters and non-procurement system notifications
Pair with Copilot Chat for cross-inbox queries: "Which vendor threads from this week have an unanswered delivery question?" to catch anything the rules miss.
Before and after — the gap in practice
Same inbox · same emails · with and without priority rules active
Returning to your inbox after a 2-hour meeting block
Without Copilot
Open inbox. 34 new emails. Scroll from the top, reading subject lines and sender names. Decide which to open first.
8–12 minutes to triage. Easy to miss a critical email buried in the middle of the list.
With Copilot
Open inbox. Four emails are marked with an up arrow. Open those first. Process the rest in order.
2 minutes to clear the high-priority queue. Nothing missed. Normal emails processed after without time pressure.
Managing a heavy end-of-week inbox
Without Copilot
60 emails. Mix of urgent, FYI, newsletters, auto-notifications, and one thread needing a decision today.
No way to know which 3 emails matter until you have read all 60. The decision email is buried in the middle.
With Copilot
High-priority queue shows 3 emails. Low-priority noise is visually separated. Decision email is at the top.
Decision made in the first 5 minutes. The rest of the inbox processed without urgency.
Starting the day across multiple active projects
Without Copilot
Arrive to 25 emails across 4 projects. No signal on which project is on fire and which is routine.
Process emails chronologically. The critical thread from Project C — sent yesterday afternoon — is seen last.
With Copilot
High-priority flags show 2 emails from Project C. Open the reasoning pane: "milestone decision requested."
Project C addressed before meetings start. Reasoning pane confirmed this was the right call.
Failure modes to expect
!
Not retroactive — existing emails are unranked
Prioritize My Inbox only applies to emails received after you enable the feature. Your existing inbox is not analysed or ranked. This is a triage tool for the inbox going forward, not a backlog processor.
Workaround: Use Copilot Chat to query your backlog — "Which emails from this week need a reply from me?" — while Prioritize handles new arrivals from that point on.
!
15-rule ceiling is a hard limit
You get 15 rules total, shared across High and Low priority. Senior roles operating across multiple domains — finance, legal, executive relationships — will hit this ceiling. There is no workaround; you have to choose which signals matter most.
Strategy: Fill High priority with 8–10 rules. Use remaining slots for your highest-volume noise sources. Leave one slot empty so you can test new rules without hitting the ceiling immediately.
!
Mobile support was cancelled
A mobile version for iOS and Android was planned for June–December 2025 and cancelled in February 2026 based on user feedback. The feature is not available on the Outlook mobile app.
If your primary email workflow is on mobile, this feature currently provides no benefit. Monitor Microsoft 365 release notes for a potential re-release.
?
Disabling a rule takes up to 24 hours
New rules activate in approximately 15 minutes. When you remove or edit a rule, the change can take up to 24 hours to take effect. The inbox may continue flagging emails under the old rule during this window.
Plan rule changes at the end of your working day if you need the inbox to behave differently by a specific time the next morning.
Rules to follow
Prepared by Mathieu Kessler · kesslernity.com
Sources: Microsoft Support — Prioritize my inbox · Microsoft Inside Track
Prioritize My Inbox · v1 · April 2026