--- title: "Outlook Add-in Overview" slug: "outlook-add-in-overview-1" description: "An overview of the Opensense Outlook Add-in for Microsoft 365, covering how it works, deployment modes, system requirements, supported environments, and key considerations before deployment." updated: 2026-03-20T14:39:22Z published: 2026-03-20T14:39:22Z canonical: "help.opensense.com/outlook-add-in-overview-1" --- > ## Documentation Index > Fetch the complete documentation index at: https://help.opensense.com/llms.txt > Use this file to discover all available pages before exploring further. # 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. It is deployed and managed by your IT, requiring no action from end users. This article explains how the add-in works, the available deployment modes and their tradeoffs, and links to all resources in this section. **Who this article is for:** IT admins configuring or managing the add-in. > [!NOTE] > End users looking to understand what the add-in does and how to use it on mobile can skip to the [End user experience](/v1/docs/outlook-add-in-overview-1#end-user-experience) section. > [!WARNING] > [**GCC High compatible**](https://www.opensense.com/gcc-high-email-signatures)**:** The Opensense Outlook Add-in is compatible with Microsoft 365 GCC High environments. Opensense connects to the Azure Government cloud infrastructure purpose-built for GCC High, allowing user data to be sourced directly from your GCC High Azure AD tenant. Additional configuration is required. See [Opensense Add-in Integration with GCC High Environments](https://help.opensense.com/docs/opensense-add-in-integration-with-gcc-high-environments) for details. ## How it works Once deployed, the Opensense Outlook 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 mode: - 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 via [Microsoft 365's Centralized Deployment](https://learn.microsoft.com/en-us/microsoft-365/admin/manage/centralized-deployment-faq?view=o365-worldwide). Your admin assigns users or groups in the Microsoft 365 Admin Center, and the add-in installs silently across Outlook Desktop, Outlook Web Access (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 requires for compliance and marketing. - **Stamping** — signatures applied entirely server-side post-send. Nothing inserted into compose. Add-in pane shows a preview of what recipients will receive. - **Plaintext block** — the add-in inserts a token into compose. Mail flow rule routes the email to Opensense for server-side transformation. Add-in pane shows a preview of what recipients will receive. Opensense's patented approach and recommended for most deployments. - **Visual preview** — full HTML signature rendered client-side in the compose window. Users can see and edit before sending. ![Plain text block vs full visual preview](https://cdn.document360.io/05b0e12d-96a6-4b75-a423-672ab2be88d7/Images/Documentation/image-1773950910903.png) Plaintext Block vs Visual Preview ### 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 post-send, where the correct HTML signature and any marketing banners are applied before delivery. - **Compliance:** Signatures are applied entirely server-side. Users cannot modify them. - **Marketing:** Full recipient-based banner targeting and advanced analytics are supported. - **End user experience:** No signature visible while composing. Employees need to understand this is expected behavior before launch. - **Best for:** Organizations that require strict signature control and can communicate the compose-window experience to employees clearly. ### Plaintext block (patented) The add-in inserts a tokenized plaintext block containing Opensense's proprietary `[[#]]` trigger into the compose window, alongside a non-clickable visual preview showing what the final rendered signature will look like. 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 plaintext block bridges the gap between stamping and visual preview: employees get a visual indicator that their signature will be applied, while the actual signature remains under server-side control. - **Compliance:** The final signature is applied server-side by Opensense. Users cannot modify the rendered output. - **Marketing:** Full recipient-based banner targeting and advanced analytics are supported. - **End user experience:** Users sees a plaintext trigger where a signature will render in the compose window. The add-in has a built-in preview of the HTML that is non-clickable and non-editable. - **Best for:** Organizations that want server-side compliance and the full marketing feature set, while giving employees visible confirmation that their signature is active. ### 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. - **Compliance:** Because the signature exists in the compose window before send, users can manually edit it — content, formatting, layout — prior to 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:** Banner targeting is limited to sender-based rules only. Recipient-based targeting is not supported. Analytics are limited to basic views and clicks; advanced banner analytics are not available. - **End user experience:** Users see and interact with a fully rendered HTML signature while composing. - **Best for:** Organizations where compose-window visibility is a priority and compliance risk and marketing limitations are acceptable tradeoffs. **Visual preview and compliance:** If your organization uses email signatures for legal disclaimers, regulatory compliance, or brand governance, review the tradeoffs carefully before choosing this mode. See [Outlook Add-in Visual Preview: Capabilities and Tradeoffs](https://help.opensense.com/docs/clone-outlook-add-in-visual-preview-limitations) for full detail. ## System requirements The Opensense Outlook Add-in requires all of the following conditions to be met. Deployments that do not meet these requirements will not function. - Mailbox hosted on **Exchange Online** (Microsoft 365). On-premises Exchange, POP, and IMAP accounts are not supported. - User licensed through **Microsoft 365 or Office 365**. Volume-based licenses (Office 2016, 2019, 2021) do not support the required API version. - Outlook client supports **Centralized Deployment** and meets minimum version requirements: - Outlook for Windows (Classic): Version 2104 (Build 13929.20296) or later, Click-to-Run only. MSI-based installs are not supported. - Outlook for Windows (New Outlook): Supported on Windows 10 Version 1809 (Build 17763) or later with a Microsoft 365 account connected to Exchange Online. New Outlook updates continuously and has no minimum build requirement. - Outlook for Mac (New Outlook): Version 16.38.506 or later. > [!CAUTION] > Legacy Outlook for Mac is not supported. - Outlook Web Access (OWA): Supported in modern browsers with a Microsoft 365 mailbox. - Outlook Mobile (iOS and Android): Supported. GCC and GCC High environments require additional configuration. - Outlook JavaScript API **v1.10 or later** required. Some features may require v1.13, available on Microsoft 365 subscriptions only. For the full compatibility matrix, see [Supported Environments for the Opensense Outlook Add-in](https://help.opensense.com/docs/supported-environments-for-the-opensense-outlook-add-in). ## 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 accordingly and add test users first to gauge propagation speed in your environment. ### Admin consent End users will be prompted to accept permissions when the add-in deploys unless an admin grants consent in advance. To avoid permission prompts disrupting employees, grant admin consent via Azure Active Directory before launch. See [Scope Users for Opensense Outlook Add-in via Microsoft 365 Admin](https://help.opensense.com/docs/clone-outlook-add-in-scope-users-for-opensense-in-m365-admin#step-3-regrant-admin-consent-for-enterprise-applications) for steps. ### 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 user group structure uses sub-groups, users must be added to a top-level group manually. ### Third-party email platforms The Outlook 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 by the add-in. For those platforms, use Opensense's routed mail flow integrations. ### Outlook Mobile — From switching limitation On Outlook Mobile, the add-in only passes the primary account context to the API. If a user switches the **From** address to an alias or shared inbox, the add-in will not update the signature to reflect the switched identity. This is a Microsoft platform limitation. ## End user experience For most employees, the Opensense Outlook Add-in requires no setup or action. Once deployed by your IT admin, the signature appears automatically when composing a new email in Outlook. Locally saved Outlook signatures are replaced or removed by the add-in. Depending on your organization's configuration, you may see: - A plaintext 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 mode) - No visible signature in the compose window, with the signature applied automatically after send (stamping mode) > [!CAUTION] > If your signature contains incorrect information, **contact your IT helpdesk or the team that manages your Opensense account**. For instructions on accessing the add-in on your mobile device, see: - [How to Access the Opensense Outlook Add-in on iOS](/v1/docs/how-to-access-opensense-outlook-add-in-on-ios) - [How to Access the Opensense Outlook Add-in on Android](/v1/docs/how-to-access-opensense-outlook-add-in-on-android) ## Article directory All Outlook Add-in documentation is organized below by topic. If you are setting up the add-in for the first time, start with **Requirements and deployment**. ### Requirements and deployment - [Supported Environments for the Opensense Outlook Add-in](https://help.opensense.com/docs/supported-environments-for-the-opensense-outlook-add-in) — minimum version requirements, supported and unsupported platforms - [Scope Users for Opensense Outlook Add-in via Microsoft 365 Admin](https://help.opensense.com/docs/clone-outlook-add-in-scope-users-for-opensense-in-m365-admin) — deploying and managing user scope in Microsoft 365 ### Configuration - [Outlook Add-in Domain Settings with Scenarios and Best Practices](https://help.opensense.com/docs/clone-outlook-add-in-domain-settings-with-scenarios-and-best-practices) — signature insertion settings, alias and shared inbox behavior, editable fields, and inline images - [Outlook Add-in Multi-Signature Selector](https://help.opensense.com/docs/clone-outlook-add-in-multi-signature-selector) — enabling and configuring multiple signatures per user - [Outlook Add-in Custom Compose Fields](https://help.opensense.com/docs/custom-compose-fields) — configuring dropdown, checkbox, and free-text fields in the compose pane (not compatible with stamping) - [Routed Key Behaviors, Limitations and Nuances](https://help.opensense.com/docs/clone-outlook-add-in-routed-key-behaviors-and-nuances) — edge cases for stamping with field edits, shared account permissions, domain switching, and manual manifest installation ### Visual preview - [Outlook Add-in Visual Preview: Capabilities and Tradeoffs](https://help.opensense.com/docs/clone-outlook-add-in-visual-preview-limitations) — what visual preview supports, compliance risks, marketing limitations, and when it makes sense to use it ### GCC and GCC High environments - [Opensense Add-in Integration with GCC High Environments](https://help.opensense.com/docs/opensense-add-in-integration-with-gcc-high-environments) — custom manifest deployment, directory sync requirements, and mobile configuration for GCC High - [Outlook Mobile Add-in within GCC and GCC High Environments](https://help.opensense.com/docs/using-the-outlook-mobile-add-in-within-gcc-environments) — enabling mobile add-ins in GCC environments where they are disabled by default ### Troubleshooting and offboarding - [Outlook Add-in Troubleshooting Guide](https://help.opensense.com/docs/clone-outlook-add-in-troubleshooting-guide) — missing add-in, permission issues, signature not applying, cache clearing, and debugging - [How to Remove the Opensense Outlook Add-in from Microsoft 365](https://help.opensense.com/docs/how-to-remove-the-opensense-add-in-from-m365-admin) ## Related articles - [How Does Opensense Work with Microsoft 365?](https://help.opensense.com/docs/how-does-opensense-work-with-office-365) - [Opensense Outlook Add-in Launch Guide](https://help.opensense.com/docs/opensense-outlook-add-in-launch-guide-everything-you-need-to-know)