No, unless it relies on Exchange Web Services (EWS). Starting October 1, 2026, Microsoft blocks EWS by default in Exchange Online, and on April 1, 2027 it removes EWS permanently. A signature tool that calls EWS is affected; ATOM Signatures does not use EWS, so it is not: it reads your directory through Microsoft Graph and inserts the signature with an Outlook add-in.
What are the dates for the end of EWS?
Microsoft published the schedule in Message Center post MC1227454, dated February 5, 2026, and repeated it on the Exchange Team blog in "Exchange Online EWS: your time is almost up", last updated October 27, 2026. Both give the same two dates.
| Date | What happens | Source |
|---|---|---|
| September 19, 2023 | Microsoft announces the retirement of Exchange Web Services in Exchange Online | Exchange Team |
| October 1, 2026 | EWS is blocked by default, unless the tenant configures an AppID AllowList and sets EWSEnabled=True | MC1227454, Exchange Team |
| April 1, 2027 | Full and permanent retirement: EWS access is permanently removed with no re-enablement, and tenant admins can no longer control EWSEnabled | MC1227454, Exchange Team |
Between the two dates, an administrator who still needs EWS can keep it with the AppID AllowList and EWSEnabled=True, as MC1227454 describes. That is a stopgap, not a plan: it ends on April 1, 2027. Microsoft's replacement for EWS is Microsoft Graph, according to the same message.
Which signature tools does the EWS shutdown affect?
The shutdown affects any application that calls EWS in Exchange Online, whatever it is used for. It does not touch tools that reach your mailboxes in another way. Two limits to keep in mind:
- Exchange Online only. MC1227454 states that the change only impacts Exchange Online; Exchange Server (on-premises) is not affected.
- It depends on the product, not on the category. "Signature software" is not an architecture. Two tools that look alike can work in completely different ways, so the answer has to come from the vendor.
As an example of a vendor tying its advice to the shutdown, Symprex's support article on OWA signatures not updating in Microsoft 365 recommends that Email Signature Manager customers upgrade to Signature 365 ahead of Microsoft disabling EWS. If you are in that situation, the guide Leaving Email Signature Manager before EWS shuts down lays out the options and the criteria to choose between them.
How do I check whether my own signature tool is affected?
Ask the vendor, in writing, and keep the answer. Five questions cover it:
- Does the product call Exchange Web Services (EWS) in Exchange Online, for any function?
- If it does, from which release does it no longer need EWS, and is that release already available to you?
- Does it ask you to add it to an AppID AllowList or to set EWSEnabled=True on your tenant? If so, what is the plan for April 1, 2027, when that setting disappears?
- Which Microsoft interface does it use instead: Microsoft Graph, an Outlook add-in, or both?
- Does it work in new Outlook, Outlook on the web, Mac, iOS and Android, or only in some of them?
If the vendor cannot answer the first question clearly, treat that as an answer. Do not wait for April 2027: from October 1, 2026, a tool that needs EWS already depends on your tenant having opted in. To compare approaches, the comparison of email signature software in Canada shows how the main tools differ.
Why is ATOM Signatures not affected?
ATOM uses two Microsoft interfaces, and neither is EWS:
- Microsoft Graph, to read the directory. ATOM reads names, titles and groups through Graph, in application mode and read-only, with the User.Read.All and GroupMember.Read.All permissions. The guide Dynamic signatures with Microsoft Graph explains how that data fills the signature.
- An Outlook add-in, to insert the signature. The add-in runs when a message is composed and calls
setSignatureAsync; Outlook decides where the signature is placed.
ATOM calls no EWS endpoint and no Exchange PowerShell. It reads no email content, and no email passes through ATOM's servers: see the architecture without mail routing. For the options Microsoft 365 offers on its own, see email signatures in Microsoft 365.
This page describes ATOM only. For every other tool, the vendor's answer is the only reliable source.
Frequently asked questions
Will my signature tool stop working when EWS is retired?
Only if it calls EWS. Microsoft blocks EWS by default in Exchange Online starting October 1, 2026, then removes it permanently on April 1, 2027. A tool that does not call EWS is not affected. Ask your vendor, in writing, whether its product uses EWS.
Can I keep EWS after October 1, 2026?
Yes, but only until April 1, 2027. According to Microsoft's message MC1227454, you must configure an AppID AllowList and set EWSEnabled to True. After April 1, 2027, EWS access is permanently removed, with no re-enablement.
Does the EWS retirement affect on-premises Exchange Server?
No. According to message MC1227454, the change only affects Exchange Online; Exchange Server (on-premises) is not affected.
Does ATOM Signatures use EWS?
No. ATOM reads the directory through Microsoft Graph, in application mode and read-only (User.Read.All and GroupMember.Read.All), and inserts the signature with an Outlook add-in. It calls neither EWS nor Exchange PowerShell, reads no email content and routes no email through its servers.
What does Microsoft replace EWS with?
Microsoft Graph. Message MC1227454 states that EWS is being retired in favor of Microsoft Graph.
Check ATOM on your own tenant. ATOM Signatures costs CA$1 per user per month, plus taxes, with a 14-day free trial.
Sources
- Microsoft Message Center — MC1227454, Exchange Online EWS retirement (published February 5, 2026): mc.merill.net
- Microsoft Exchange Team blog — Exchange Online EWS: your time is almost up: techcommunity.microsoft.com
- Microsoft Exchange Team blog — Retirement of Exchange Web Services in Exchange Online (September 19, 2023): techcommunity.microsoft.com
- Symprex — OWA signatures are not updating in Microsoft 365: support.symprex.com
Sources consulted on November 2, 2026.