How to add an email signature in Outlook

Updated 2026-08-05

Outlook stores signatures differently depending on which version you use, which is why a signature that works on your desktop often disappears on your phone. This guide covers all four places you need to set it, and what to do when the signature loses its formatting.

New Outlook for Windows and Outlook on the web

New Outlook and Outlook on the web share the same signature store, so setting it in one place applies it to the other automatically. The signature lives on your Microsoft 365 mailbox rather than on the machine.

1. Open Settings from the gear icon in the top-right corner.
2. Go to Mail, then Compose and reply.
3. Under Email signature, give the signature a name.
4. Paste your signature into the editor. Copy it from the rendered preview, not from the HTML source, so the formatting carries over.
5. Choose whether to apply it to new messages, replies and forwards, or both.
6. Select Save.

The web editor strips some CSS. If your layout collapses, the signature is likely relying on CSS that Outlook removes — see the HTML best practices guide below.

Classic Outlook for Windows

Classic Outlook keeps signatures as files on disk, in three parts: an .htm file, a .txt fallback, and a folder holding the images. Because the images are referenced from that folder, copying only the .htm file to another machine produces a signature with broken image placeholders.

1. Go to File, then Options, then Mail, then Signatures.
2. Select New and name the signature.
3. Paste the rendered signature into the edit box.
4. Set the default signature for new messages and for replies and forwards.
5. Select OK.

The signature files live in %APPDATA%\Microsoft\Signatures. Dropping a prepared .htm file plus its matching image folder there installs a signature without any manual pasting — which is how bulk deployment works.

Outlook for Mac

Outlook for Mac stores signatures locally in the app profile. Signatures do not sync from the Windows client, so they must be set once per machine.

1. Open Outlook, then Settings, then Signatures.
2. Select the plus button to add a signature.
3. Paste the rendered signature and name it.
4. Assign it as the default for your account under Choose default signature.

Outlook for iOS and Android

The mobile apps only support plain text signatures. There is no way to set an HTML signature with a logo directly in the app. Replies composed on mobile will use this plain text version, so keep it short — usually a name, title, and phone number.

If your organisation needs a consistent HTML signature on mobile too, it has to be applied server-side with an Exchange transport rule, which appends it to messages as they leave the server.

1. Open the app and tap your profile icon.
2. Tap the gear icon to open Settings.
3. Tap Signature.
4. Replace the default text and confirm.

When the signature loses its formatting

Three causes account for almost every broken signature. First, the message is being composed in plain text rather than HTML — check the Format Text tab. Second, the signature was copied from HTML source instead of from a rendered page, so Outlook pastes the markup as visible text. Third, the layout uses modern CSS such as flexbox or grid, which the Word rendering engine behind Outlook for Windows does not support.

The generator produces table-based, inline-styled markup specifically to avoid the third case.