Once EWS is gone, Email Signature Manager can be replaced by any signature approach that does not depend on EWS. There are four routes: Signature 365, the product Symprex recommends to its own customers; an Outlook add-in built on event-based hooks; a server-side mail flow rule; or Microsoft's native signatures. The right one depends on the Outlook clients you must cover, on replies and forwards, on images and on your budget.
Why are Email Signature Manager customers looking at alternatives?
Two things came together. First, Symprex's support article OWA signatures are not updating in Microsoft 365 states that Microsoft enabled roaming signatures on all Microsoft 365 tenants in April 2023, and that Email Signature Manager is unable to update OWA signatures when roaming signatures are enabled. It adds that version 10.1 or later is required for OWA signatures to work with Exchange Online.
Second, Symprex recommends in that same article that customers upgrade to Signature 365 before Microsoft disables the Exchange Web Services (EWS) API in Exchange Online. Microsoft's own dates are October 1, 2026 for the default block and April 1, 2027 for the permanent end: see EWS retirement: will your email signature tool stop working? for the table and the sources. Everything below about Symprex comes from its own article; this page makes no claim about how either of its products works inside.
What can replace Email Signature Manager?
Four routes, described neutrally. Each has a source for what it does and for what it cannot do.
| Route | What it is | Limits to check | Source |
|---|---|---|---|
| Signature 365 (Symprex) | The upgrade Symprex recommends. According to Symprex, it is designed for Microsoft 365, supports Outlook on all platforms including mobile and new Outlook, lets you migrate Email Signature Manager settings directly, and has special pricing for existing customers | These are Symprex's statements: ask for a trial and check them against your own clients | Symprex |
| Client-side add-in | An Outlook add-in that inserts the signature as the message is composed, built on the event-based signature API that Microsoft recommends to independent software vendors | Depends on each vendor: clients covered, replies, mobile, how the directory is read | Microsoft Learn |
| Server-side rule | A mail flow (transport) rule that adds the signature or disclaimer to the message in transit | You can't insert the signature directly under the latest reply or forward; users can't see server-side signatures in their Sent Items folder; you can't embed images in the signature | Microsoft Learn |
| Microsoft's native signatures | Signatures that users create in Outlook, stored in the mailbox (roaming signatures) so they follow the account across devices | Built for one person's devices, not for consistency across employees; the admin-side cmdlet stops working while roaming signatures are on (see the PowerShell signature guide) | Microsoft Support |
Microsoft's page on server-side signatures notes that "some of these limitations can be overcome by using non-Microsoft tools". For how the server-side route works step by step, read signatures with an Exchange transport rule.
How do I choose a replacement?
Put the same questions to every candidate, in writing, and compare the answers side by side:
| Criterion | The question to ask |
|---|---|
| EWS | Does the product call EWS in Exchange Online? If so, what is the plan for April 1, 2027? |
| Replies and forwards | Where does the signature land in a reply or a forward, and can the reply version be shorter than the original? |
| Sent Items | Does the sender see the signature in the Sent Items folder? |
| Images | Are logos and banners shown, and how are they delivered: linked or embedded? |
| Clients covered | Which of the following does it cover: Outlook for Windows (classic and new), Outlook on the web, Mac, iOS, Android? |
| Roaming signatures | Does it work while Microsoft's roaming signatures are enabled, which is the default? |
| Migration | Can your existing signatures, assignments and rules be imported, or must they be rebuilt? |
| Data and privacy | What data does it read from your tenant, where is it hosted, and does any email pass through its servers? |
| Price | What is the price per user, and is there a minimum number of users? |
The first row is the one with a deadline. For a side-by-side view of the main products on these points, see the comparison of email signature software in Canada.
What are the steps of a migration?
- List what exists today: the signatures, who gets which one, and any rules that depend on groups or departments.
- Save the HTML of each signature and the images it uses, so that nothing has to be redrawn from memory.
- Put the questions of the table above to two or three candidates, including Signature 365 if you want to stay with Symprex.
- Run a pilot with one group, on every Outlook client your staff use, including a reply and a forward on a phone.
- Switch everyone over well before April 1, 2027, then retire the old tool once nobody depends on it.
If part of your fleet is moving to the new Outlook, read the new Outlook signature guide at the same time: roaming signatures change where signatures are stored.
Where does ATOM Signatures fit?
ATOM is one product in the client-side add-in route, and it is not the only reasonable choice. Its facts, so that you can set them against the criteria above:
- It calls no EWS endpoint and no Exchange PowerShell. It reads the directory through Microsoft Graph, in application mode and read-only (User.Read.All and GroupMember.Read.All), reads no email content and relays no email.
- The add-in inserts the signature with
setSignatureAsyncas the message is composed; Outlook decides where it is placed. - On desktop and web, the reply and forward versions can be set to identical, compact, custom or none. On phones, ATOM works in Outlook for iOS and Android 4.2352.0 or later with Microsoft 365 accounts.
- It does not lock the native signature: ATOM does not call
disableClientSignatureAsync. - The minimum is one seat: CA$1 per user per month, plus taxes, with a 14-day free trial.
For the mobile side, read Outlook signature on Mac and mobile.
Frequently asked questions
What replaces Email Signature Manager once EWS is gone?
A tool that does not depend on EWS. There are four routes: moving to Signature 365, which Symprex recommends, an Outlook add-in built on event-based hooks, a server-side mail flow rule, or Microsoft's native signatures. The right choice depends on the Outlook clients to cover, replies and forwards, images and your budget.
Does Symprex recommend a replacement?
Yes. In its support article, Symprex recommends upgrading to Signature 365, which is designed for Microsoft 365. Also according to Symprex, Email Signature Manager settings can be migrated directly and special pricing is available for existing customers.
What are the limits of a server-side signature?
According to Microsoft Learn, you can't insert the signature directly under the latest reply or forward, users can't see server-side signatures in their Sent Items folder, and you can't embed images. Microsoft adds that some of these limitations can be overcome by using non-Microsoft tools.
When do I need to have chosen a replacement?
By April 1, 2027 at the latest, when Microsoft permanently removes EWS. Starting October 1, 2026, EWS is blocked by default in Exchange Online, unless your tenant has chosen to keep it.
Try ATOM alongside your current tool. ATOM Signatures costs CA$1 per user per month, plus taxes, with a 14-day free trial.
Sources
- Symprex — OWA signatures are not updating in Microsoft 365 (roaming signatures, version 10.1, Signature 365): support.symprex.com
- Microsoft Message Center — MC1227454, Exchange Online EWS retirement: mc.merill.net
- Microsoft Learn — Create email signatures and disclaimers with mail flow rules (limits of server-side signatures): learn.microsoft.com
- Microsoft Learn — Set-OrganizationConfig (event-based signature API for ISVs): learn.microsoft.com
- Microsoft Support — Outlook roaming signatures: support.microsoft.com
Sources consulted on November 2, 2026.