Spell check is on by default in Outlook, but you may need to turn it back on if it was disabled

Outlook checks your spelling and grammar as you type, marking errors with red and blue underlines. If you are not seeing these underlines, spell check is likely turned off. The steps to turn it back on depend on which version of Outlook you use — the web version, the desktop app for Windows, or the app for Mac each have slightly different settings.

The good news is that spell check in Outlook works the same way it does in Word: it catches misspelled words, some grammar issues, and flags words it does not recognize. You can add words to your dictionary so Outlook stops marking them as errors, and you can ignore individual flagged words without changing your settings.

Key Takeaways

  • Outlook spell check is on by default and marks errors with red underlines for spelling and blue underlines for grammar as you type.
  • In Outlook on the web, spell check cannot be turned off — it runs automatically in the compose window.
  • In Outlook desktop for Windows, go to File > Options > Mail > Spelling and turn on "Check spelling as you type" and "Mark my comments and revisions."
  • In Outlook for Mac, go to Tools > Spelling and Grammar > Spelling and Grammar Preferences and check "Check spelling as you type."
  • You can right-click any underlined word to see suggestions, ignore it, or add it to your dictionary so Outlook stops flagging it.

Turn on spell check in Outlook on the web

If you use Outlook through your web browser at outlook.com or through your work account, spell check is always on and cannot be disabled. You do not need to change any settings. As you type a message, Outlook marks misspelled words with a red underline and grammar issues with a blue underline.

Right-click any underlined word to see correction suggestions. You can click a suggestion to replace the word, click "Ignore" to skip it this time, or click "Add to dictionary" to tell Outlook to stop flagging that word in the future.

Turn on spell check in Outlook for Windows

Open Outlook and go to File in the top left corner. Click Options at the bottom of the menu. In the Outlook Options window, click Mail on the left side.

Scroll down until you see the Spelling section. Check the box next to Check spelling as you type. If you want Outlook to also flag grammar issues, check Mark my comments and revisions as well. Click OK at the bottom of the window to save your changes.

Spell check will now run as you type. If you do not see underlines appearing under misspelled words, close Outlook completely and open it again — sometimes the change does not take effect until you restart the program.

Turn on spell check in Outlook for Mac

Open Outlook and click Tools in the menu bar at the top of your screen. Click Spelling and Grammar, then click Spelling and Grammar Preferences.

In the window that opens, make sure the box next to Check spelling as you type is checked. You can also check Check grammar if you want Outlook to flag grammar issues in addition to spelling. Click the close button (the red circle in the top left corner) to save your changes and close the window.

What to do when Outlook flags a word you know is correct

Outlook uses a built-in dictionary, but it does not know every word — especially proper nouns, technical terms, or words from other languages. When Outlook underlines a word that is spelled correctly, right-click it and click Add to Dictionary. Outlook will stop flagging that word in all future messages.

If you only want to ignore the word in the current message, right-click it and click Ignore or Ignore All. This tells Outlook to skip that word for this message only. The next time you use the word in a different message, Outlook will flag it again unless you add it to your dictionary.

Check spelling before you send a message

Spell check as you type catches most errors, but you can also run a full spelling check before sending. In Outlook for Windows, go to Review in the ribbon at the top and click Spelling and Grammar. In Outlook for Mac, click Tools in the menu bar and click Spelling and Grammar. In Outlook on the web, spell check runs automatically and you cannot run a separate check.

The spelling check window will open and show you each flagged word one at a time. You can choose to replace it with a suggestion, ignore it, or add it to your dictionary. Click OK when the check is complete.

Frequently Asked Questions

Why is spell check not working even after I turned it on?

Close Outlook completely and open it again. Sometimes the setting does not take effect until you restart the program. If spell check is still not working, go back to the spelling settings and make sure the box is actually checked — it may have reverted to off.

Can I turn off spell check in Outlook?

In Outlook for Windows and Mac, you can turn off spell check by unchecking "Check spelling as you type" in the spelling settings. In Outlook on the web, spell check cannot be turned off — it is always on.

Does Outlook spell check work in all languages?

Outlook can check spelling in multiple languages, but you need to set your language first. In Windows, go to File > Options > Language and select your language. In Mac, go to Tools > Language Preferences. Outlook will then check spelling based on that language's dictionary.

What is the difference between the red and blue underlines?

Red underlines mark spelling errors — words that are misspelled or not in Outlook's dictionary. Blue underlines mark grammar issues, like incomplete sentences or incorrect word usage. Not all versions of Outlook show blue underlines by default.