You switched to the new Outlook for Windows and your signature is gone — or it no longer matches your colleagues' signatures? It is not a bug: the new Outlook handles signatures differently from the classic version. A signature is no longer a file on the PC but a setting stored in the Microsoft 365 mailbox. This guide explains what changes, what stops working — GPO, scripts, COM add-ins — and how to keep one consistent signature across the organization.
%APPDATA%\Microsoft\Signatures folder: signatures are stored in the Microsoft 365 mailbox and follow the account from one device to another. Signatures deployed by GPO or script, and COM add-ins, do not work there; to enforce the same signature for everyone, you need an event-based web add-in deployed by the administrator.
Why did my signature disappear in the new Outlook?
Classic Outlook saves each signature as three files (.htm, .rtf and .txt) in the user's Windows profile, plus a folder for images. The new Outlook does not read those files. It only shows the signatures saved in the account's Microsoft 365 mailbox.
Since version 2303, classic Outlook automatically copies to the mailbox the signatures set as the default for new messages and for replies and forwards. Those signatures show up again in the new Outlook. The others stay on the PC, under "Signatures on this device", and do not follow the user — which is why some signatures seem to vanish after the switch.
A third common case: the signature was dropped in place by a GPO or a logon script. Since the new Outlook never read those files, the signature simply never existed there.
Where does the new Outlook store the signature?
In the mailbox, in the cloud. Microsoft calls this roaming signatures: a signature created on one device is available on every device where the same account is configured, without recreating it.
Roaming signatures come with three limits worth knowing:
- Microsoft 365 mailboxes only. Accounts hosted on Exchange on-premises, with a third-party provider, or set up as POP or IMAP do not sync their signature.
- A per-user setting. Each person creates and edits their own signature; the administrator has no native way to enforce or update it.
- The end of tools that wrote the old format. Microsoft notes that third-party signature roaming add-ins, which relied on unpublished Outlook data structures, no longer work.
For an organization, roaming signatures solve consistency across one person's devices — but not consistency across employees.
Classic vs new Outlook: what changes for signatures?
| Item | Classic Outlook | New Outlook for Windows |
|---|---|---|
| Where the signature is stored | Files in the Windows profile (and the mailbox since version 2303) | Microsoft 365 mailbox only |
| Deployment by GPO or script | Yes, on domain-joined PCs | No |
| COM and VSTO add-ins | Yes | No |
| Event-based web add-ins | Yes | Yes |
| Same signature on all of one person's devices | Partial | Yes, for Microsoft 365 mailboxes |
| Signature enforced by the organization | Through GPO, on Windows only | Through a web add-in only |
What stops working with the new Outlook?
Three common ways of managing signatures stop working in the new Outlook:
- GPO and logon scripts. They copy files into
%APPDATA%\Microsoft\Signaturesand write theNewSignatureandReplySignatureregistry values. The new Outlook reads neither. The method and its limits are covered in the Outlook signature via GPO guide. - COM and VSTO add-ins. Microsoft states they are not supported in the new Outlook for Windows and keep working only in classic Outlook. When settings are imported, Outlook installs the web counterpart instead, if the vendor publishes one.
- Tools that edited the local signature. Any software that generated the PC's signature files no longer affects what the user sees in the new Outlook.
Web add-ins, on the other hand, work unchanged: it is the same model as in Outlook on the web, on Mac and on mobile.
How do I get my signature back in the new Outlook?
For a single user, the steps are short:
- Open Settings, then Accounts and Signatures.
- If several accounts are set up, pick the one the signature applies to.
- Check whether the signature is already there: it will be if it was set as the default in an up-to-date classic Outlook.
- Otherwise, select Add signature, name it and recreate it. To save time, open the old
.htmfile from the Signatures folder in a browser and copy its content. - Tick the boxes to apply it to new messages and to replies and forwards.
Be careful with copy and paste: pasted images are often embedded in the message rather than hosted, which makes them show up as attachments for the recipient. See Outlook signature image not showing.
At the scale of an organization, this approach does not hold: it assumes every employee recreates their signature correctly, then updates it every time a title, phone number or logo changes.
When does the new Outlook become mandatory?
Microsoft's documentation does not give a date. The page Stages of migration to new Outlook for Windows (Microsoft Learn, updated February 23, 2026) splits the migration into three stages and commits to advance notice, but it sets no date for moving to opt-out or to cutover. Here is what it does establish:
| Stage | New Outlook | Switching back to classic Outlook | Notice to administrators |
|---|---|---|---|
| 1. Opt-in | Off by default; users try it with the toggle at the top right of classic Outlook | Possible | Not specified |
| 2. Opt-out | On by default; users are brought into it automatically | Possible, if needed | At least 12 months before this stage, for managed Enterprise plans |
| 3. Cutover | New deployments of Outlook with a Microsoft 365 subscription include the new Outlook | Not possible | At least 12 months before this stage, in Production rings |
Microsoft adds that it will use its existing channels to publish a "notice of disruptive change" 12 months before moving to opt-out and cutover in the production rings. The stage that applies to your tenant is therefore announced in the Microsoft 365 Message center, not on that page. As for classic Outlook, existing installations, perpetual or subscription, remain supported until at least 2029.
The practical consequence: a fleet can run classic and new Outlook side by side for several years. Whatever signature method you choose must work in both.
What the timeline changes for signatures
- A GPO or script signature stops working machine by machine. It works as long as the user stays in classic Outlook; as soon as they move to the new Outlook — on their own in stage 1, by default in stage 2 — it disappears from their messages (see what stops working). A gradual migration therefore leaves some employees with the organization's signature and others without for months.
- Roaming signatures do not change in nature. In the new Outlook, the signature lives in the Microsoft 365 mailbox and remains a per-user setting. To turn roaming signatures off in Outlook on the web and the new Outlook, Microsoft provides the
PostponeRoamingSignaturesUntilLaterparameter; the details are in the guide on Set-MailboxMessageConfiguration not setting the signature. - Microsoft recommends that signature vendors build on event-based add-ins. The ATOM Signatures add-in is one: it inserts the signature when the message opens using
setSignatureAsync(Outlook chooses the position), in the new Outlook and in classic Outlook alike, regardless of which stage your organization is in.
How do I enforce the same signature for everyone in the new Outlook?
The only centralized method compatible with the new Outlook is an event-based web add-in. Its OnNewMessageCompose event fires when a new message, reply or forward is opened; the add-in then inserts the organization's signature. According to Microsoft Learn, this event is supported in the new and classic Outlook for Windows, Outlook on the web, Outlook for Mac, iOS and Android. That is what lets you centrally manage email signatures in Office 365, the new Outlook included.
Two conditions apply:
- Deployment by the administrator. Microsoft specifies that an event-based add-in only launches automatically when it is deployed from the Microsoft 365 admin center, under Integrated apps. See deploying an Outlook signature to the whole organization.
- Standard compose surfaces. In the new Outlook and Outlook on the web, event-based activation targets standard message windows; it may not fire on special surfaces, such as replying to a meeting invite with a note.
With this architecture, the signature is built from the directory (Microsoft Graph data), targeted by Microsoft 365 group, individual user or shared mailbox, and updated once for everyone. The add-in runs inside Outlook: the email is never routed through a third-party server.
IT checklist before the migration
- Inventory how signatures are deployed today: GPO, script, COM add-in, web add-in or manual entry.
- Confirm that mailboxes are hosted in Microsoft 365, a prerequisite for roaming signatures.
- Replace the GPO and COM add-ins with an event-based web add-in.
- Deploy the add-in centrally from the Microsoft 365 admin center, under Integrated apps.
- Test the signature with a pilot group in the new Outlook, classic Outlook, Outlook on the web and on mobile.
- Watch the Microsoft 365 Message center for the date when the new Outlook becomes the default experience in your organization.
Related reading: the signature missing or misplaced in a reply.
Frequently asked questions
Why did my signature disappear in the new Outlook?
Because the new Outlook does not read the signature files that classic Outlook saved on the PC. It only shows signatures stored in the Microsoft 365 mailbox. A signature that was not set as the default for new messages or replies stayed on the old PC and has to be recreated.
Where does the new Outlook store signatures?
In the user's mailbox, in the cloud. Microsoft calls this roaming signatures: the signature follows the account to every device where it is configured. It works with Microsoft 365 and Outlook.com mailboxes, not with Exchange on-premises or POP and IMAP accounts.
Does a GPO-deployed signature work in the new Outlook?
No. The GPO copies files into the Signatures folder of the Windows profile and writes registry values that only classic Outlook reads. The new Outlook ignores those files and keys, so the signature does not appear.
Do signature add-ins work in the new Outlook?
Web add-ins do; COM and VSTO add-ins do not. Microsoft states that COM add-ins are not supported in the new Outlook for Windows. An event-based web add-in deployed by the administrator inserts the signature at compose time in the new Outlook, classic Outlook, Outlook on the web, Mac and mobile.
On what date does the new Outlook become mandatory?
Microsoft's Learn documentation gives no date. It describes three stages (opt-in, opt-out, cutover) and promises administrators at least 12 months of notice before opt-out and before cutover. Your organization's stage is announced in the Microsoft 365 Message center.
How long will classic Outlook be supported?
Microsoft states that existing installations of classic Outlook will remain supported until at least 2029. Organizations on managed Enterprise plans will get at least 12 months of notice before the new Outlook becomes the default, and again before the switch back to classic is removed.
A signature that survives the migration. ATOM Signatures inserts the same signature in the new Outlook, classic Outlook, the web, Mac, iPhone and Android — client-side, with 100% Canadian hosting. $1 per user per month, plus taxes, with a 14-day free trial.
Go further: the complete Microsoft 365 email signature guide, Outlook signatures on Mac and mobile and ATOM vs the native Microsoft 365 signature.
Sources
- Microsoft Learn — Stages of migration to new Outlook for Windows (updated February 23, 2026): learn.microsoft.com
- Microsoft Support — Outlook roaming signatures: support.microsoft.com
- Microsoft Learn — Activate add-ins with events (updated September 1, 2026): learn.microsoft.com
- Microsoft Learn — Migrate from COM add-ins to web add-ins: learn.microsoft.com
- Microsoft Support — How to add and change an email signature in Outlook: support.microsoft.com
Sources accessed September 17, 2026; migration timeline rechecked November 3, 2026.