How to Set Up AI-Powered Email Triage in Microsoft 365 for a Small UK Professional Services Firm

The average professional services worker receives 121 emails a day. At a 20-person UK firm, that is 2,420 messages landing in inboxes every working day — and the overwhelming majority need no immediate action. Microsoft 365 now includes two AI-powered ways to sort that pile before anyone opens a single message. Copilot's Prioritize My Inbox feature ranks email by inferred importance. Power Automate flows classify and route messages using AI Builder prompts. Both work without writing code, but they solve different problems and cost different amounts. Here is how to decide which one your firm needs, how to set each up, and what UK data protection law says about processing client email with AI.

Why Email Triage Matters More for Professional Services Than Any Other Sector

A 2025 workplace email study found the average business user receives 121 emails and sends 40 each day. Professional services firms — accountants, solicitors, consultants, architects — sit at the heavy end of that range because every client engagement generates its own email thread, and missing a deadline buried in paragraph four of a forwarded chain has real consequences.

81 per cent of UK small and medium businesses rely on email as their primary client communication channel. The problem is not volume alone. It is that urgent client requests, internal admin, marketing newsletters, and compliance notices all arrive in the same inbox with no indication of priority.

Manual triage — scanning subject lines, skimming the first paragraph, deciding what to act on — takes an estimated 28 per cent of the average knowledge worker's day. AI email triage does not eliminate that work entirely, but it moves the sorting step to before you open anything, and it gets more accurate the longer you use it.

Two Approaches — Copilot Prioritize My Inbox vs Power Automate Flows

Microsoft shipped two distinct tools for email triage in 2025, and they serve different purposes.

Copilot Prioritize My Inbox is a per-user feature inside Outlook. It went into public preview in February 2025, reached general availability in April 2025 for new Outlook for Windows and Outlook on the Web, and requires a Microsoft 365 Copilot licence. It ranks every incoming message as high, normal, or low priority based on the sender's relationship to you, their job title, the email content, and whether it requires action. High-priority emails get an up-arrow marker in the message list. You can filter your inbox to show only high-priority items. Copilot also shows a short explanation of why it ranked each message the way it did.

You can customise the ranking rules in Settings > Copilot > Prioritize — telling it to always prioritise messages from a specific client, about a specific project, or containing specific terms like "deadline" or "overdue."

Power Automate email classification is a flow-based approach that works at the shared mailbox or organisational level. When a new email arrives, a Power Automate flow passes its subject and body to an AI Builder prompt that classifies it into categories you define — for example, urgent client request, new enquiry, internal admin, invoicing, marketing. The flow then routes the email to the right Teams channel, applies a category label, creates a task in Planner, or forwards it to a specific person.

The key difference: Copilot Prioritize works per user and requires no setup beyond enabling it. Power Automate works across shared mailboxes and teams but requires you to design the flow and write the classification prompt.

What It Costs for a 20-Person UK Firm

Pricing depends on which approach you use and what Microsoft 365 plan you already have.

Microsoft 365 Business Premium costs £16.90 per user per month. It includes Exchange Online, Outlook, Teams, SharePoint, and advanced security features. It does not include Copilot.

Microsoft 365 Copilot is an add-on at £16.10 per user per month at full price. A promotional rate of £13.80 per user per month ran until March 2026. For a 20-person firm, that is £322 per month at full price on top of the Business Premium cost — a total of £660 per month for both.

Power Automate Premium costs £11.60 per user per month for the people who build and manage flows. But you do not need a licence for every user — only the flow owner needs a Premium licence if the flow runs on a shared mailbox. One licence at £11.60 per month can triage email for the entire firm if the flow runs against a shared mailbox like info@yourfirm.co.uk.

For a firm that wants AI triage on shared inboxes without giving every user Copilot, the Power Automate route costs 96 per cent less: £11.60 per month versus £322 per month.

Step by Step — Setting Up Copilot Prioritize My Inbox

1. Confirm every user has a Microsoft 365 Copilot licence assigned in the Microsoft 365 admin centre.
2. Open new Outlook for Windows or Outlook on the Web.
3. Go to Settings > Copilot > Prioritize.
4. Toggle Prioritize My Inbox to On.
5. Add custom rules — specify people, projects, or keywords that should always rank as high priority.
6. Return to the inbox. High-priority messages now show an up-arrow icon. Click the Copilot filter to view only high-priority items.
7. Review the priority explanations for the first week and adjust your custom rules based on what Copilot gets right and wrong.

The feature learns from your behaviour over time. If you consistently open and reply to messages from a particular sender within minutes, Copilot will start ranking that sender higher.

Step by Step — Building a Power Automate Email Classification Flow

1. Go to make.powerautomate.com and sign in with your Microsoft 365 account.
2. Create a new automated cloud flow.
3. Set the trigger to When a new email arrives in shared mailbox (V2) and select your shared mailbox address.
4. Add a Compose action to combine the email subject and body into a single text block.
5. Add a Run a prompt action from the AI Builder connector.
6. Write your classification prompt. A working example: "Classify this email into one of these categories: urgent_client, new_enquiry, internal_admin, invoicing, marketing, spam. Return only the category name. Email content: [the combined text output from step 4]."
7. Add a Switch action that branches based on the AI Builder response.
8. In each branch, add the action you want — post to a Teams channel, create a Planner task, apply a category label, or forward to a specific person.
9. Save and test with a sample email. Check the flow run history for errors.
10. Once working, set the flow to On and monitor for the first week.

The AI Builder prompt included with Power Automate Premium handles the classification. You do not need to train a model or label training data — the prompt approach uses the underlying language model directly.

What UK GDPR Says About Processing Client Email With AI

If your firm processes client email through Copilot or Power Automate, you are using AI to process personal data. The emails contain names, contact details, case references, and in professional services, client confidential information.

Three things matter under UK GDPR. First, you need a lawful basis for the processing. Legitimate interest is the strongest basis for this purpose — you have a legitimate interest in triaging email efficiently, and the processing is proportionate to that aim. But you need to document this in a Legitimate Interest Assessment.

Second, your privacy policy needs to mention AI-assisted email processing. If clients send email to your firm and that email is classified by an AI model, they have a right to know. A single paragraph in your privacy policy explaining that incoming email is automatically categorised to improve response times is enough.

Third, data residency matters. Microsoft 365 data for UK tenants is stored in Microsoft's UK data centres (UK South and UK West regions). Copilot processing for UK tenants stays within the EU Data Boundary, which includes the UK. Confirm this in your Microsoft 365 admin centre under Settings > Org settings > Organization profile > Data location.

Five Mistakes Small Firms Make With AI Email Triage

1. Giving every user Copilot when only the shared mailbox needs triage. If the goal is sorting the info@ or enquiries@ mailbox, one Power Automate Premium licence at £11.60 per month does the job. You do not need to spend £322 per month on 20 Copilot licences.

2. Not testing the classification prompt with real email. AI Builder prompts classify based on the wording you give them. If your prompt says "urgent_client" but your actual urgent emails say "ASAP" or "deadline tomorrow," the model may not catch them. Test with 50 real emails before going live.

3. Skipping the privacy policy update. Automated email processing is a processing activity under UK GDPR. If your privacy policy does not mention it, you are non-compliant. The fix takes 15 minutes.

4. Routing without a fallback. If the AI Builder prompt returns an unexpected category or fails to classify an email, the flow needs a default branch that sends unclassified email to a person for manual review. Without it, messages get lost.

5. Forgetting that Copilot Prioritize was removed from Outlook mobile. Microsoft pulled the Prioritize My Inbox feature from Outlook for iOS and Android in February 2026 following user feedback. If your team relies on mobile email, Power Automate classification with Teams notifications is a more reliable approach.

A Practical Checklist Before You Go Live

1. Audit your current Microsoft 365 plan — confirm whether you are on Business Basic, Standard, or Premium, and check which licences are assigned in the admin centre.
2. Decide whether you need per-user triage (Copilot) or shared-mailbox triage (Power Automate) — or both.
3. If using Copilot, assign licences and enable Prioritize My Inbox for a pilot group of five users before rolling out firm-wide.
4. If using Power Automate, define your email categories based on how your firm actually works — not how you think it should work. Review 100 recent emails from your shared mailbox and sort them into groups.
5. Write and test your AI Builder classification prompt with real email content. Aim for 90 per cent accuracy before going live.
6. Update your privacy policy to mention automated email categorisation.
7. Document your legitimate interest assessment for AI-assisted email processing.
8. Confirm your Microsoft 365 data residency is set to the UK in the admin centre.
9. Set up a default route for unclassified email so nothing gets lost.
10. Monitor classification accuracy for the first two weeks and refine your prompt or Copilot rules based on what it gets wrong.