K-MailSign
Switch on the Outlook add-in for everyone in Microsoft 365
Microsoft has no way for apps to write Outlook signatures, so a small K-MailSign add-in inserts them when someone writes an email. Your admin adds it once; staff do nothing.
Last updated
What you need
- A Microsoft 365 global admin account
- The Owner, Administrator or IT administrator role in K-MailSign
- Employees with a licence and a saved company default signature
- For phones and other apps: a Windows PC with PowerShell (optional)
Add the add-in in Microsoft 365
- Click Integrations in the sidebar.
- Under Switch on the Outlook add-in for everyone, click Generate Outlook add-in.
- Click Copy link.
- Click Open Integrated apps. The Microsoft 365 admin centre opens.
- Choose Upload custom apps, then Office Add-in.
- Choose Provide link to the manifest file, paste the link and click Validate.
- Assign it to the Entire organisation and click Deploy.
Publish the signatures
- Click Sync & history.
- Click Sync now, or click New deployment and choose Microsoft 365.
- Ask a colleague to start a new email in Outlook and check the signature.
Cover phones and other mail apps (server-side signatures)
- On Integrations, find All devices: server-side signatures.
- Click Download the setup script.
- Run it once in PowerShell as your Microsoft 365 admin.
- Click I have run the script.
- Run the script again after you change or deploy signatures, or add people.
Good to know
- The add-in works in Outlook on the web, new Outlook, and Outlook for Windows and Mac. It can take a few hours to appear (Microsoft says up to 24).
- Outlook shows a new signature on the next new email, reply or forward after a sync.
- Server-side rules skip messages the add-in already signed, so nobody gets two signatures. Mail never passes through K-MailSign.
- To stop everything, click Remove K-MailSign from Microsoft 365…, type REMOVE and confirm. Employees and designs are kept.
Common errors
The signature does not appear in Outlook
The add-in can take up to 24 hours after your admin deploys it. Check that the person has a licence and that you pressed Sync now.
"No published signatures yet. Deploy signatures to Microsoft 365 first."
Open Sync & history and click Sync now, or run a New deployment to Microsoft 365. Then download the script again.
"Microsoft directory sync is not configured on this server yet. The Outlook add-in works without it."
Skip Sign in with Microsoft. Add employees by hand or with Import CSV / Excel, and use the add-in.
Outlook stopped adding signatures after I clicked Rotate key
Rotate key stops the current add-in. Copy the new link and upload the add-in again in Integrated apps.
Sync says Microsoft refused to save changes
The K-MailSign app needs the User.ReadWrite.All permission with admin consent. Microsoft also blocks apps from editing other administrators’ profiles; change those in the Microsoft 365 admin centre.
Still stuck?
Email hello@khanals.in with the app name, what you clicked and the exact message you saw. Do not send passwords, PINs or authenticator codes. You can also use the contact page.