Reading-pane & compose add-ins
Task panes that read the open message, inject content into a reply, and act when the user sends.
Outlook
Outlook Plugin Development
Outlook add-in development creates tools that operate in supported reading, compose, and event-based Outlook contexts using Office.js and, where required, Microsoft Graph. It is intended for organizations that need email or calendar workflows, CRM context, validation, or internal actions available from Outlook, with features limited by the client and Mailbox requirement set.
What I build
What is included in Outlook add-in development?
Event-based activation
Add-ins that run on new-message or on-send without the pane open — auto-tagging, disclaimers, and on-send checks.
Microsoft Graph mail & calendar
Reading and writing mail, events, categories, and attachments through the Microsoft Graph API.
CRM & helpdesk context
Showing the sender's contact, deal, or ticket data on the open email, and logging emails back with one click.
Problems this solves
What problems can Outlook add-in development solve?
- Reps copy-pasting email details into a CRM all day.
- No context about the sender inside Outlook, so staff switch tabs to look them up.
- Disclaimers or categories that should be applied automatically on send but aren't.
- A requirement that the add-in behave the same in Outlook desktop, web, and Mac.
Example use cases
What does Outlook add-in development look like in practice?
One-click CRM logging
An add-in that logs the open email to HubSpot with the contact matched via Microsoft Graph — no copy-paste.
On-send disclaimer
Event-based activation appends a legal disclaimer and checks for missing attachments the moment a user hits Send.
Support context pane
The reading pane shows the customer's open tickets and recent orders next to their email.
Tech stack
What technologies power Outlook add-in development?
Core
- Office.js (Mailbox API)
- TypeScript
- React
Activation
- Event-based activation
- On-send handlers
Data
- Microsoft Graph
- RoamingSettings
- MSAL SSO
Delivery
- Manifest
- AppSource
- Centralized deployment
Process
How does Outlook add-in development work?
01
Define the trigger
Reading pane, compose, or on-send — and what data it needs.
02
Build with Office.js
Mailbox API, Graph calls, and persisted settings.
03
Test hosts
Verify on Outlook desktop, web, and Mac.
04
Publish
AppSource or centralized deployment for the org.
Outlook is one host in my wider Microsoft 365 development work. For the other Office apps, start from Office plugin development.
Related services
Microsoft 365 Developer
Microsoft 365 development creates add-ins and integrations for supported Outlook, Word, Excel, and PowerPoint clients using Office.js, Microsoft Graph, and Entra ID. It is intended for organizations that need to place business workflows inside Microsoft 365 or connect Microsoft data to another system, with compatibility determined by each host and requirement set.
Office Plugin Development
Office add-in development creates web-based task panes, ribbon commands, and document or workbook tools for supported Word, Excel, Outlook, and PowerPoint clients. It is intended for organizations replacing manual Office workflows or assessing whether a legacy VSTO or COM plugin can move to Office.js, subject to the APIs available in each host.
Excel Add-in Developer
Excel add-in development creates custom functions, task panes, worksheet automation, and API-connected data workflows using Office.js. It is intended for organizations that need calculations, reporting, imports, or two-way data synchronization inside supported Excel clients, with availability determined by platform and requirement set.
FAQ
Questions, answered
- Can the add-in work in both Outlook desktop and web?
- Yes — a single Office.js add-in runs in Outlook on Windows, Mac, and the web (and new Outlook), with checks where an API isn't available on a given host.
- Can it run without the task pane open — for example on send?
- Yes, using event-based activation. The add-in can run on new message or on send to auto-tag, add disclaimers, or validate before the email leaves.
- Can it read and send mail through Microsoft Graph?
- Yes. I use the Microsoft Graph API for mail and calendar — reading messages, creating events, applying categories, and handling attachments with the right permissions.
- Can it show our CRM data on the open email?
- Yes — a common build. The add-in matches the sender and pulls their contact, deal, or ticket data from your CRM into the reading pane.
- How is an Outlook add-in installed across a company?
- Through AppSource or, more often for internal tools, centralized deployment in the Microsoft 365 admin center so it appears for everyone automatically.
Let's build it together
Email me with what you need — I'll reply with a clear plan and next steps. Prefer chat? WhatsApp works too.