Outlook Add-in overview

Overview

The Opensense Outlook Add-in is a centrally managed Microsoft 365 Integrated App that automatically applies your company’s email signatures to every email composed in Outlook, on desktop, web, and mobile. Your IT team deploys and manages it, and end users don’t need to do anything.

This article is for IT admins who configure or manage the add-in. It explains how the add-in works, the deployment methods and their tradeoffs, and links to all the articles in this section.

End users

To learn what the add-in does and how to use it on mobile, go to End user experience.

GCC High compatibility

The Opensense Outlook Add-in is compatible with Microsoft 365 GCC High environments. Opensense connects to the Azure Government cloud infrastructure built for GCC High, so user data is sourced directly from your GCC High Azure AD tenant. Additional configuration is required. See Opensense Outlook Add-in integration with GCC High environments.

How it works

Once deployed, the add-in loads automatically when a user opens a new compose window in Outlook, and inserts their assigned signature. How that signature is handled depends on your deployment method:

Client-side

The signature is sent directly with the email from Outlook.

Server-side stamping

The signature is cleared from the compose window before the email is sent, and Opensense's servers apply the signature during routing.

The add-in is deployed through Microsoft 365’s Centralized Deployment. Your admin assigns users or groups in the Microsoft 365 admin center, and the add-in installs silently across Outlook desktop, Outlook on the web (OWA), and Outlook Mobile.

Deployment methods

The add-in supports three deployment methods. The right choice depends on how much compose-window visibility your employees need, and how much server-side control your organization needs for compliance and marketing.

• Server-side, after send Stamping

  Signatures are applied entirely server-side after send. Nothing is inserted into compose.

  • The add-in pane shows a preview of what recipients will receive
• Recommended Plain Text Block

  The add-in inserts a token into compose. A mail flow rule routes the email to Opensense for server-side transformation.

  • The add-in pane shows a preview of what recipients will receive
  • Opensense's patented approach, recommended for most deployments
• Client-side, in compose Visual Preview

  The full HTML signature is rendered client-side in the compose window.

  • Users can see and edit it before sending

Comparing the methods

Feature	Stamping	Plain Text Block	Visual Preview
Compliance	Signatures are applied entirely server-side. Users cannot modify them.	The final signature is applied server-side by Opensense. Users cannot modify the rendered output.	Users can edit the signature (content, formatting, layout) before sending. Those edits bypass Opensense servers entirely, and are not tracked or blocked. This is a meaningful compliance risk for organizations with signature governance requirements.
Marketing	Full recipient-based banner targeting and advanced analytics.	Full recipient-based banner targeting and advanced analytics.	Sender-based banner targeting only; recipient-based targeting is not supported. Analytics are limited to basic views and clicks.
End user experience	No signature visible while composing. Employees need to understand this is expected behavior before launch.	A plain text trigger where the signature will render, plus a built-in preview of the HTML that is non-clickable and non-editable.	A fully rendered HTML signature that users see and interact with while composing.
Best for	Organizations that require strict signature control and can explain the compose-window experience to employees clearly.	Organizations that want server-side compliance and the full marketing feature set, while giving employees visible confirmation that their signature is active.	Organizations where compose-window visibility is a priority, and the compliance risk and marketing limits are acceptable tradeoffs.

For each method’s strengths and limitations, and help choosing one, see Comparing Outlook Add-in deployment methods.

Server-side stamping with add-in signature removal

The add-in removes any locally saved Outlook signatures before the email is sent. No signature is visible in the compose window. The email routes through Opensense’s servers after send, where the correct HTML signature and any marketing banners are applied before delivery.

Plain Text Block (patented)

The add-in inserts a tokenized plain text block containing Opensense’s proprietary [[#]] trigger into the compose window, alongside a non-clickable visual preview of the final rendered signature. When the email is sent, a mail flow rule detects the [[#]] token and routes the message to Opensense, where it is transformed server-side into the full HTML signature before delivery.

The best of both

The Plain Text Block bridges the gap between Stamping and Visual Preview: employees see that their signature will be applied, while the actual signature stays under server-side control.

Visual Preview

The add-in renders a live HTML signature directly inside the Outlook compose window. The signature is inserted client-side before the email is sent.

Visual Preview and compliance

If your organization uses email signatures for legal disclaimers, regulatory compliance, or brand governance, review the tradeoffs carefully before you choose this method. See Outlook Add-in Visual Preview capabilities and tradeoffs.

System requirements

The add-in needs Exchange Online, a supported Microsoft 365 or Office 365 license, and an Outlook client that meets the minimum version for Centralized Deployment. MSI-based installs and volume-licensed Office versions (Office 2016, 2019, and 2021) are not supported, because they don’t support the required API version.

For the full version table, platform support matrix, and unsupported environments, see Outlook Add-in supported environments.

Key deployment considerations

Propagation time

After a user or group is added to the add-in's deployment scope in Microsoft 365, it can take up to 72 hours for the add-in to appear in Outlook. Plan your rollout timeline for this, and add test users first to gauge propagation speed in your environment.

Admin consent

End users are prompted to accept permissions when the add-in deploys, unless an admin grants consent in advance. To avoid prompts that disrupt employees, grant admin consent in Azure Active Directory before launch. See Scoping Outlook Add-in users in the Microsoft 365 admin center.

Nested groups are not supported

Microsoft does not support nested groups for Centralized Deployment. Users must be directly assigned to a top-level Microsoft 365 group. If your group structure uses sub-groups, add the users to a top-level group manually.

Third-party email platforms

The add-in only applies signatures to emails composed in Microsoft Outlook. Emails sent through third-party platforms such as Outreach, Salesloft, or Salesforce are not covered. For those platforms, use Opensense's routed mail flow integrations.

Outlook Mobile From switching

On Outlook Mobile, the add-in passes only the primary account context to the API. If a user switches the From address to an alias or shared inbox, the add-in does not update the signature for the switched identity. This is a Microsoft platform limitation, and it applies to all deployment methods.

End user experience

For most employees, the add-in needs no setup or action. Once your IT admin deploys it, the signature appears automatically when you compose a new email in Outlook. The add-in replaces or removes locally saved Outlook signatures.

Depending on your organization’s configuration, you see one of these:

• A plain text block in the compose window, with a non-clickable preview of your formatted signature
• A fully rendered HTML signature in the compose window (Visual Preview)
• No visible signature in the compose window, with the signature applied automatically after send (Stamping)

Incorrect information in your signature?

Contact your IT helpdesk or the team that manages your Opensense account.

To use the add-in on your mobile device, see Using the Opensense Outlook Add-in on iOS or Using the Opensense Outlook Add-in on Android.

Article directory

All Outlook Add-in documentation, by topic. If you’re setting up the add-in for the first time, start with Requirements and deployment.

Requirements and deployment

• Outlook Add-in supported environmentsMinimum version requirements, and supported and unsupported platforms.
• Scoping Outlook Add-in users in the Microsoft 365 admin centerDeploy the add-in and manage user scope in Microsoft 365.

Configuration

• Configuring the Outlook Add-in in Domain SettingsSignature insertion settings, alias and shared inbox behavior, editable fields, and inline images.
• Setting up multiple signatures in the Outlook Add-inTurn on and set up multiple signatures per user.
• Setting up Custom Compose Fields for the Outlook Add-inDropdown, checkbox, and free-text fields in the compose pane. Not compatible with Stamping.
• Expected behaviors in routed Outlook Add-in deploymentsEdge cases for Stamping with field edits, shared account permissions, domain switching, and manual manifest installation.

Visual Preview

• Outlook Add-in Visual Preview capabilities and tradeoffsWhat Visual Preview supports, compliance risks, marketing limits, and when it makes sense.

GCC and GCC High environments

• Opensense Outlook Add-in integration with GCC High environmentsCustom manifest deployment, directory sync requirements, and mobile configuration for GCC High.
• Outlook mobile add-ins in GCC and GCC High environmentsTurn on mobile add-ins in GCC environments, where they are off by default.

Troubleshooting and offboarding

• Troubleshooting the Outlook Add-inMissing add-in, permission issues, signature not applying, cache clearing, and debugging.
• Removing the Outlook Add-in in the Microsoft 365 admin centerRemove users, or the add-in, from Microsoft 365.

What’s next

• How does Opensense work with Microsoft 365?
• Outlook Add-in launch guide