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How to add a signature in Outlook for Mac, new and legacy

Add a signature in Outlook for Mac, make it the default for new messages and replies, and check your app before legacy Outlook for Mac stops in October 2026.
The Sendoff team4 min read

In Outlook for Mac, open Settings from the Outlook menu, then choose Mail and Signatures. Create the signature, close the window, and insert it with the Signature button when you write a message. Legacy Outlook for Mac uses Email instead of Mail in the same place. Microsoft says the legacy app stops working with Exchange Online mailboxes from October 2026, so check which one you run first.

Which Outlook for Mac you have

Microsoft's article has two tabs, Outlook for Mac and Legacy Outlook for Mac. The steps are close, but a few names differ. If the Signatures page sits under Mail, you have the current app. If it sits under Email, you have the legacy app.

Create a signature

  1. On the Outlook menu, select Settings.
  2. Under Mail, select Signatures.
  3. Select Untitled and rename the default signature.
  4. Select the add button to create another one, and type its name.
  5. In the signature editor, type your details. Select text before you format it, or the formatting may land on the wrong words.
  6. To add a logo, a photo or a table, select See more items (...).
  7. Close the Signatures window.

Insert it into a message

Click in the body of the message. On the Ribbon, select Signature, then choose one from the list. If the button is missing, select See more items (...), or add it to your toolbar. Microsoft covers that in its article on customizing the toolbar.

Make it the default for new messages and replies

  1. On the Outlook menu, select Settings, then under Mail, select Signatures.
  2. Under Set default signature, select the account.
  3. Set For new messages and For replies or forwards to the signatures you want.
  4. Repeat this for each account. Microsoft says a default has to be set separately for every account.
  5. Close the Signatures window.

Legacy Outlook for Mac

On the Outlook menu, select Settings, then under Email, select Signatures. Double-click Untitled and type a name, or select the add button to create one. In the editor, add your text and any picture or table, then close the editor. To insert a signature, click in the message body, then on the Message tab select Signature. To set a default, go to Choose default signature under Email, pick the account, and set New messages and Replies/forwards.

Check the app before October 2026

Microsoft's end-of-support article says that, starting October 2026, the legacy client "will stop working against Exchange Online mailboxes." It also says Exchange Web Services (EWS) "will be retired on October 1, 2026." The legacy app keeps working with Exchange On-Premises mailboxes until October 9, 2029.

If you use legacy Outlook for Mac with a Microsoft 365 mailbox, move to the current app before the cutoff. Then open Signatures on the new app and check the default for each account. Do not assume the old setup came across.

Fixes for problems people report

These come from Microsoft Q&A threads. They are community answers, not official fixes, except where a Microsoft moderator confirmed a build.

  • The default reverts to None (version 16.108). A thread opened on April 17, 2026 says the default setting went back to None every time the window closed. A Microsoft moderator could not reproduce it on 16.108. The steps they gave were to check that the correct account is selected, then fully quit and reopen Outlook before you test again.
  • Replies leave out the original message (legacy app, version 16.110). Posted June 22, 2026. The accepted answer says to update to 16.110.1 on the Current Channel, or to go back to 16.109.3. A moderator confirmed a fix in 16.111.1 on July 28, 2026. Note your build number before you update or roll back.
  • The signature lands below the reply attribution. Community answers describe this after recent updates. It is the same problem covered in our guide to different reply signatures, so the reply-placement workarounds are there.
  • The logo or photo does not show. That is an image problem, not a signature-setting problem. See why Outlook signature images do not show.

How Sendoff handles this

Sendoff builds the signature as table-based HTML with inline CSS and hosted images. Copy puts the formatted version on your clipboard, ready to paste into Outlook's signature editor. The size meter shows the HTML length against Gmail's 10,000-character limit, which helps when the same signature also goes into Gmail. Outlook setup steps are on the Outlook integration page.

Sources

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