ATOM Signatures applies your organization's official signature to every email sent from Outlook, across Microsoft 365 (formerly Office 365). You build the signature once in a console, target it by group, and the Outlook add-in inserts it on its own, on desktop, on the web and on mobile. The email itself never leaves Microsoft 365.
Try it on your own Microsoft 365 tenant. Setup is done from an admin account, with nothing to install on workstations.
Not ready yet? See how it works in four steps, further down this page.
Why does native Office 365 signature management fall short?
Microsoft 365 has no central signature management for Outlook. The native methods work for a simple case, then run into the same walls as the organization grows:
- One signature per user. Each employee sets their own in Outlook, and versions drift apart: outdated titles, stretched logos, missing notices. The new Outlook also changed where signatures are stored. See signatures in the new Outlook.
- GPOs and logon scripts: Windows only. A Group Policy prepares a signature in classic Outlook for Windows, but leaves the web, Mac and mobile out. See the Outlook signature via GPO.
- Exchange transport rules: a signature the sender never sees. It is added on the server after sending: missing from Sent Items, often unreliable with images, and added again on every reply. See transport rule signatures.
- Mobile. Outlook on iPhone and Android keeps its own signature, set device by device and often reduced to plain text. See the Outlook signature on Mac and mobile.
Each method, with its steps, is covered in the Microsoft 365 email signature guide.
How does Office 365 email signature management work with ATOM?
In four steps, with no heavy IT project: connect Microsoft 365, build your signatures, deploy the add-in, then let every email go out signed:
- Connect Microsoft 365. An admin grants read-only access to the directory through Microsoft Entra.
- Build your signatures. In the visual editor, with dynamic fields (name, title, phone) and group targeting.
- Deploy the add-in. Once, for the whole organization, from the Microsoft 365 admin center (Integrated apps). Nothing to install on the user side.
- It's signed, everywhere. Every email goes out with the right signature, inserted while composing. Employees have nothing to do.
After deployment, Microsoft can take up to 24 hours to roll out the add-in (up to 72 hours on mobile). The full procedure is in the documentation.
Client-side, not server-side
There are two ways to add a signature: place it in Outlook while the message is being written (client-side), or have a relay server add it after sending (server-side). ATOM Signatures is a client-side tool: the add-in inserts the signature into the draft, so the sender sees it before sending, then in Sent Items.
What stays the same in your mail flow
ATOM Signatures is not a mail relay. There is no outbound connector, no Exchange transport rule and no MX record change: the email never leaves Microsoft 365. The body and subject of your emails are never sent to ATOM. Only the links in the signature and banners go through our domain to count clicks, and this tracking can be turned off in Settings.
What is not covered
The trade-off is real, and it is worth knowing before you choose:
- Emails sent outside Outlook do not get the signature: business or third-party apps sending over direct SMTP, multifunction printers, unmanaged devices, and email clients other than Outlook.
- Exchange on-premises is not supported: you need Exchange Online mailboxes.
- On mobile, the signature is inserted while composing, but it is not checked again on send, and the internal or external signature does not switch based on recipients.
For a detailed comparison of the two architectures, see client-side or server-side signatures.
Email signature management features
Centralized deployment
One admin consent and one add-in deployment cover the whole organization. The signature then applies on its own in Outlook on Windows (classic and new Outlook), on the web, on Mac, on iPhone and on Android.
Targeting by groups, people and shared mailboxes
Each department gets its own signature, assigned by Microsoft 365 group, security group or distribution list. A priority decides between signatures when a person belongs to several groups, and a direct assignment to a person or a shared mailbox takes precedence over the group. See Microsoft 365 group signatures.
Up-to-date data via Microsoft Graph
Signature fields are filled from the directory: name, title, department, phone numbers, and up to 15 extension attributes. A title change in Microsoft 365 shows up in the signature, with no manual edit. See dynamic signatures with Microsoft Graph.
Visual editor
Logos, tables, colours and HTML, with a preview filled with a real user's data. A separate version can apply to replies and forwards.
Outlook mobile
The same add-in applies the signature in Outlook on iPhone and Android: new messages, replies and forwards. Mobile coverage relies on your organization's own manifest, generated in the console's Connections tab.
Internal or external signature
In Outlook on Windows, on the web and on Mac, the signature changes based on recipients: one version for your colleagues, another for outside contacts. A signature can also depend on the employee's language, with scheduled start and end dates.
Banners and A/B tests
A banner below the signature, targeted by group, shared mailbox or signature, scheduled, with up to three A/B variants. The click rate is aggregated, without identifying who clicked. Included at no extra charge.
Satisfaction surveys
Three faces, a 0 to 10 score (NPS) or five stars: the recipient answers in one click from the email they received. Results and comments arrive in the console, and a widget shows the average rating on your website.
vCard, QR code and booking links
A vCard and a QR code to save the sender's contact details, a booking link (Bookings, Calendly…) and a Google reviews link. The employee's photo from Microsoft 365 is available as an option.
Audit logs
Sensitive actions are recorded in an append-only log: console sign-ins, creation, modification and deletion of signatures, logo uploads, billing changes. No function of the application modifies or deletes an entry.
Security and data residency
ATOM Signatures reads the directory in read-only mode, after an admin's consent: Microsoft Graph application permissions User.Read.All and GroupMember.Read.All, limited to users and groups. The service requests no permission to access mailbox content, and never writes to the directory.
Configuration data is hosted in Canada, and isolation between organizations is enforced at the database level. Under Quebec's Law 25, ATOM acts as a mandatary: your organization remains responsible for the information, and we claim no third-party certification. Hosting, subprocessors and retention periods are detailed on the Trust and security page.
Pricing
| Plan | Price |
|---|---|
| Standard, monthly billing | CA$1 / user / month |
| Standard, annual billing | CA$12 / user / year |
| Nonprofits and public sector | CA$0.75 / user / month, on request |
Plus tax. Every feature is included, with no tiers and no paid add-ons. MSPs and resellers set their own price, from $0.75 per seat: see the MSP and reseller program. Billing details are on the pricing page.
Compared with other tools
Evaluating several email signature managers? Our comparisons set ATOM Signatures against each one, feature by feature: ATOM vs Exclaimer, ATOM vs CodeTwo, ATOM vs Letsignit, ATOM vs Signitic and, against Microsoft's own tools, ATOM vs the native Microsoft 365 signature.
If you are already leaving a tool, the alternatives pages describe the options and the migration, step by step.
Office 365 email signature management FAQ
How do I centrally manage email signatures in Office 365?
Use a central signature manager such as ATOM Signatures: you build the signature once in a console, assign it by group, and an Outlook add-in deployed for the whole organization inserts it into every email. Microsoft 365 (formerly Office 365) has no native central signature management: otherwise you set up each device by hand, use a GPO (Windows only) or an Exchange transport rule (signature added after sending). Fields are filled from the directory through Microsoft Graph, and the add-in is deployed once from the Microsoft 365 admin center.
Can I manage Outlook signatures without a GPO or login script?
Yes. An event-based Outlook add-in, deployed centrally from the Microsoft 365 admin center, inserts the signature with no GPO, logon script or per-device setup. That is what ATOM Signatures does, and it also covers the web, Mac and mobile, which a GPO never reaches. The new Outlook for Windows no longer reads signatures placed by GPOs or scripts: there, an event-based add-in is the only compatible centralized method.
Does it work with Exchange Online and the new Outlook?
Yes. ATOM Signatures works with Exchange Online mailboxes, in the new Outlook for Windows, classic Outlook for Windows (recent Microsoft 365 versions), Outlook on the web, Outlook for Mac and Outlook mobile. In the new Outlook, an event-based add-in is the only compatible centralized method, since signatures placed by GPOs or scripts are no longer read. Exchange on-premises is not supported.
Does it work on Outlook mobile?
Yes, in Outlook on iPhone and Android: the signature is inserted in new messages, replies and forwards, with no action from employees. Mobile coverage relies on your organization's own manifest, generated in the console's Connections tab. On mobile, the signature is applied while composing only (it is not checked again on send), the internal or external signature does not switch based on recipients, and the add-in rollout can take up to 72 hours.
Do our emails go through your servers?
No. The signature is inserted in Outlook, client-side: no relay, no connector, no transport rule and no MX change, and the email never leaves Microsoft 365. ATOM never receives the body or subject of your emails: the add-in only sends the sender's address, any shared mailbox, the platform and, on send on desktop and web, only the recipients' domains. Signature links go through our domain to count clicks, and this tracking can be turned off. The trade-off: an email sent outside Outlook, by an app over direct SMTP or a multifunction printer, does not get the signature.
What permissions does it require?
Read-only Microsoft Graph application permissions: User.Read.All and GroupMember.Read.All, granted through an admin's consent. No permission gives access to mailbox content, and ATOM never writes to the directory. Setup requires a Global administrator or Exchange administrator account.
Does it help with Quebec's Law 25?
Yes: ATOM Signatures is designed to help your organization meet Quebec's Law 25. Configuration data is hosted in Canada, directory access is read-only, no email content is read, audit logs are append-only and the right to erasure is built in. ATOM acts as a mandatary: your organization remains responsible for its personal information, and a data processing agreement (DPA) is available on request.
How much does it cost?
CA$1 per user per month, or CA$12 per user per year, plus tax, with every feature included. Nonprofits and the public sector pay CA$0.75 per user per month, on request. The free trial lasts 14 days: a card is requested at sign-up, but nothing is charged during the trial. A user is a distinct sender address, and a shared mailbox used through the service does not consume a seat.
A consistent signature on every email, starting this week. Every feature, hosted in Canada, $1 per user per month.
Questions before you start? Email us at info@atomsolutions.ca.