Outlook signatures do not always sync across every Outlook app. New Outlook and Outlook.com use account-based signature settings, classic Outlook for Windows stores signatures locally, and the mobile app has its own separate signature field.
Does this affect you?
Use this for classic Outlook for Windows, new Outlook, Outlook.com, and Outlook mobile on iPhone or Android when one account shows different signatures on different devices.
Set the signature in Outlook on the web or new Outlook
Use this as the master copy if you use Outlook.com or new Outlook.
- Open Outlook.com or the new Outlook app.
- Click Settings.
- Go to Mail > Compose and reply.
- Type or paste the signature in Email signature.
- Use the editor for links, formatting, and images if needed.
- Choose the default signature for new messages, replies, and forwards.
- Click Save.
This account-based signature should appear in Outlook.com and new Outlook when you sign in with the same account.
Copy it into classic Outlook for Windows
Classic Outlook stores signatures on the computer, so it needs its own setup.
- Open File > Options > Mail.
- Click Signatures.
- Click New and name the signature.
- Paste the same signature text and formatting.
- Choose the account and set defaults for new messages and replies/forwards.
- Click OK.
Repeat this on each computer that uses classic Outlook. The setting is local to that installation.
Set the mobile signature
Outlook mobile uses a separate signature setting.
- Open the Outlook app.
- Tap your profile picture or initials.
- Tap Settings.
- Select the mail account if you use more than one.
- Tap Signature.
- Turn on the signature option if needed and enter your text.
More control
Use one master version
Because the storage systems are separate, keep the web or new Outlook signature as your master copy and copy it into classic Outlook and mobile after changes.
Check for organization-managed signatures
A Microsoft 365 administrator can apply centralized signatures that do not appear in your personal signature settings. If yours keeps changing, ask IT whether a mail-flow signature is being applied.
Insert images separately
Logo images may not copy cleanly between Outlook versions. Save the image file and insert it directly in each signature editor instead of relying on copy and paste.
Use shorter reply signatures
Outlook versions often let you choose different signatures for new mail and replies. A full signature for new messages and a shorter one for replies keeps long threads cleaner.
Sources
- Microsoft Support – Create and add an email signature in Outlook (2025)
- Microsoft Support – Create and add an email signature in Outlook.com (2025)
- Microsoft Support – Add or change an email signature in Outlook mobile (2025)