Summary

This article shows you how to use color categories and follow-up flags in Outlook to visually organize your emails, calendar events, contacts, and tasks. Categories let you tag items with color-coded labels (e.g., "Project Alpha," "Urgent," "Waiting for Response"), while flags add reminders so important items do not slip through the cracks.

In this guide

• 1. Understand Categories vs. Flags
• 2. Create and Customize Categories
• 3. Apply a Category to an Email
• 4. Apply a Category to Calendar Events or Contacts
• 5. Filter and Sort by Category
• 6. Flag an Email for Follow-Up
• 7. Set Up a Quick Click Flag
• 8. Combine Categories and Flags for a Complete System

Before You Start

• A Microsoft 365 account with Outlook access.
• Outlook Desktop (Classic or New), Outlook on the Web, or Outlook Mobile.

Instructions

1. Understand Categories vs. Flags

The two look similar and do different jobs, so it helps to know which one fits what you are tracking.

Feature	Categories	Flags
Purpose	Color-coded labels for grouping and filtering	Reminders and follow-up tracking
Works on	Emails, calendar events, contacts, tasks	Emails only
Visual indicator	Colored square next to the item	Flag icon next to the item
Reminder support	❌	✅ (set a due date and reminder)
Multiple per item	✅ (an email can have multiple categories)	❌ (one flag per email)
Appears in To Do	❌	✅ (flagged emails sync to Microsoft To Do)

Tip: Use categories for classification ("what type of thing is this?") and flags for action ("I need to follow up on this").

2. Create and Customize Categories

The default categories are named by color, which tells you nothing — rename them for the work you actually do.

Outlook Desktop (Classic)

1. Go to the Home tab and click Categorize > All Categories.
2. The Color Categories dialog shows the default categories (each with a color).
3. To rename a category: select it and click Rename. Give it a meaningful name (e.g., "Project Alpha," "Client Follow-Up," "Read Later").
4. To change the color: select the category and click a color from the palette.
5. To add a new category: click New, enter a name, choose a color, and optionally assign a shortcut key.
6. Click OK to save.

Outlook on the Web

1. Click the Settings gear icon (top right) > View all Outlook settings.
2. Go to General > Categories.
3. Click + Create category, enter a name, and choose a color.
4. Click Save.

New Outlook (Desktop)

1. Click the Settings gear icon > Categories.
2. Create, rename, or delete categories.

3. Apply a Category to an Email

Tagging an email takes a couple of clicks, and a keyboard shortcut takes it down to one.

1. Select the email (or open it).
2. Click Categorize in the ribbon (or right-click the email > Categorize).
3. Select the category you want to apply.
4. The colored category tag appears next to the email in your message list.
5. To apply multiple categories, repeat the process — an email can have as many categories as you need.

Tip: Assign keyboard shortcuts to your most-used categories for instant tagging. In the All Categories dialog, assign shortcuts like Ctrl + F2, Ctrl + F3, etc.

4. Apply a Category to Calendar Events or Contacts

Categories are not limited to emails — you can apply them to calendar events and contacts too.

Calendar Events

1. Open the calendar event.
2. Click Categorize in the event ribbon.
3. Select a category. The event appears in the calendar with the category's color.

Contacts

1. Open a contact.
2. Click Categorize and select a category.
3. You can then filter your contact list by category.

5. Filter and Sort by Category

Once you have categorized your emails, you can filter your inbox to show only items with a specific category.

Outlook Desktop

1. In the message list, click View > View Settings > Filter (or Sort).
2. Use the Categories criteria to filter by a specific category.
3. Alternatively, click the Categories column header in the message list to sort all emails by category.

Outlook on the Web

1. Click the Filter button at the top of the message list.
2. Select a category from the filter dropdown.

Search by Category

1. In the Outlook search bar, type category:"Project Alpha" (replace with your category name).
2. Outlook shows only items tagged with that category.

6. Flag an Email for Follow-Up

Flags add a visual reminder and sync with Microsoft To Do, so flagged emails appear in your task list.

1. In your inbox, hover over the email.
2. Click the flag icon that appears on the right side of the message row.
3. The email is flagged with a default "Follow up" reminder.
4. The flagged email now appears in Microsoft To Do under the Flagged email list.

Set a Specific Due Date

1. Right-click the flag icon on the email.
2. Select a timeframe:
   • Today — Due today, reminder at end of day.
   • Tomorrow — Due tomorrow.
   • This Week — Due by end of the current week.
   • Next Week — Due by end of next week.
   • Custom — Set a specific start date, due date, and reminder time.

Mark as Complete

1. Click the flag icon again to mark the follow-up as complete.
2. The flag changes to a checkmark, and the task is marked as done in To Do.

7. Set Up a Quick Click Flag

If you flag emails frequently, set a default flag so a single click applies your preferred timeframe.

1. In Outlook Desktop: right-click the flag column header and select Set Quick Click.
2. Choose the default flag type (e.g., Today, Tomorrow, This Week).
3. Click OK. Now a single click on the flag icon applies that default.

8. Combine Categories and Flags for a Complete System

Categories say what something is and flags say when you will deal with it.

For maximum organization, use both features together:

Email Type	Category	Flag
Client request requiring a response	"Client" (blue)	Flag for Today
Project update — read later	"Project Alpha" (green)	No flag (informational)
Waiting for someone else's reply	"Waiting" (yellow)	Flag for Next Week
Urgent issue from management	"Urgent" (red)	Flag for Today with reminder
Newsletter to review when free	"Read Later" (purple)	No flag

Troubleshooting

TIP

If you are new to categories, start with 5–7 categories that match your actual workflow (e.g., by project, client, or action type). Too many categories creates overhead — keep it simple and consistent.

Symptom / Error	Potential Cause	Solution
Categories do not sync between devices	Category names differ between desktop and web	Create categories in Outlook on the Web — these sync to all devices. Desktop-only categories may not sync.
Flagged emails do not appear in To Do	To Do is not connected to your Outlook account	Open Microsoft To Do and sign in with the same work account. Flagged emails should appear under Flagged email.
Category colors look different on web vs. desktop	Color palettes differ slightly between clients	Choose colors that are distinct enough to be recognizable across all platforms.
Cannot see the Categories column	Column is hidden in the message list	Right-click the column headers in Outlook Desktop and check Categories to show the column.
Flag reminder does not appear	Reminder time has passed or reminders are disabled	Right-click the flag > Custom and set a future reminder time. Check File > Options > Advanced > Reminders to ensure they are enabled.

Related Articles

• How to Create Email Rules in Outlook
• How to Use Focused Inbox in Outlook
• How to Use Microsoft To Do for Personal Task Management
• How to Set Up an Out-of-Office Reply in Outlook

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