AI assistance right inside Outlook, even with Exchange Server on your own hardware.
Microsoft 365 Copilot needs a mailbox in Exchange Online. If you run your own Exchange, you have been left out so far. Our add-in brings the assistant to where you already work. It sits as its own tab in the ribbon and as a sidebar on the main window. That sidebar stays open whether you are in the inbox, in the calendar or in any other folder. You do not need an open message for it.
What this looks like day to day
Real screenshots from our lab, with made-up example data. You can talk to the assistant in every view, on an open message, in the calendar and first thing in the morning for a look at the day ahead.
The interface follows the language of Outlook. Available in German, English, Spanish, French, Italian, Portuguese, Japanese, Chinese and Korean.
What an assistant for Exchange on-premises has to be able to do
Microsoft 365 Copilot requires a mailbox in Exchange Online. And Claude, ChatGPT, Perplexity and the other providers only give you a task pane on the open item. We work in every view and take whatever is open at that moment as the context.
| Criterion | Postgate AICOM and web add-in | Microsoft 365 Copilotin Outlook | Other AI add-insClaude, ChatGPT, Perplexity and others |
|---|---|---|---|
| Works with Exchange Server on your own hardware | Postgate AI: The normal case for us. Access over EWS to your own server, be it 2016, 2019, Subscription Edition or hybrid | Microsoft 365 Copilot: Needs a mailbox in Exchange Online. For servers of your own there has so far only been an interest survey | Other AI add-ins: The task pane loads, but it only sees the open item and not the mailbox |
| There in every Outlook view, with no message open | Postgate AI: A sidebar on the main window, open in the inbox, in the calendar, in people and in every folder | Microsoft 365 Copilot: A chat pane in Outlook, but only for mailboxes in Exchange Online | Other AI add-ins: The Office add-in model starts the task pane on the open item |
| Relates to the view you have open right now | Postgate AI: The message you are reading, the part of the calendar you see or the message list goes into the question as context | Microsoft 365 Copilot: Relates to messages and appointments, provided the mailbox sits in the cloud | Other AI add-ins: Only the open message |
| Tools that work on the whole mailbox | Postgate AI: More than 90 tools, among them search, folders, rules, tasks, contacts, rooms, free and busy times and creating appointments | Microsoft 365 Copilot: Summaries, drafts and meeting suggestions within the cloud services | Other AI add-ins: Text in, text out. No access to folders, rules or the calendar |
| Free choice of language model | Postgate AI: Anthropic, OpenAI-compatible, Mistral, OpenRouter or an endpoint of your own, set per tenant | Microsoft 365 Copilot: Microsoft decides the model | Other AI add-ins: Whichever model the provider runs |
| A model in your own network (Ollama, vLLM) | Postgate AI: With the self-hosted licence, mailbox and model both stay with you, even without internet access | Microsoft 365 Copilot: A pure cloud service | Other AI add-ins: Pure cloud services |
| Access with the permissions of the signed-in user | Postgate AI: No shared service account, no full access to other people’s mailboxes | Microsoft 365 Copilot: Works in the context of the signed-in user | Other AI add-ins: They only see what the user has opened |
| Rollout without a Microsoft 365 licence | Postgate AI: An MSI through group policy, the manifest from the Exchange Management Shell. A Microsoft account is possible, but not a condition | Microsoft 365 Copilot: A Copilot licence per user, on top of the Microsoft 365 licence | Other AI add-ins: The approval works on-premises too, but the account sits with the provider |
| Interface in nine languages | Postgate AI: German, English, Spanish, French, Italian, Portuguese, Japanese, Chinese and Korean, each matching the language of Outlook | Microsoft 365 Copilot: Multilingual | Other AI add-ins: Depends on the provider |
Works with Exchange Server on your own hardwarePostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: The normal case for us. Access over EWS to your own server, be it 2016, 2019, Subscription Edition or hybrid
Microsoft 365 Copilot: Needs a mailbox in Exchange Online. For servers of your own there has so far only been an interest survey
Other AI add-ins: The task pane loads, but it only sees the open item and not the mailbox
There in every Outlook view, with no message openPostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: A sidebar on the main window, open in the inbox, in the calendar, in people and in every folder
Microsoft 365 Copilot: A chat pane in Outlook, but only for mailboxes in Exchange Online
Other AI add-ins: The Office add-in model starts the task pane on the open item
Relates to the view you have open right nowPostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: The message you are reading, the part of the calendar you see or the message list goes into the question as context
Microsoft 365 Copilot: Relates to messages and appointments, provided the mailbox sits in the cloud
Other AI add-ins: Only the open message
Tools that work on the whole mailboxPostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: More than 90 tools, among them search, folders, rules, tasks, contacts, rooms, free and busy times and creating appointments
Microsoft 365 Copilot: Summaries, drafts and meeting suggestions within the cloud services
Other AI add-ins: Text in, text out. No access to folders, rules or the calendar
Free choice of language modelPostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: Anthropic, OpenAI-compatible, Mistral, OpenRouter or an endpoint of your own, set per tenant
Microsoft 365 Copilot: Microsoft decides the model
Other AI add-ins: Whichever model the provider runs
A model in your own network (Ollama, vLLM)Postgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: With the self-hosted licence, mailbox and model both stay with you, even without internet access
Microsoft 365 Copilot: A pure cloud service
Other AI add-ins: Pure cloud services
Access with the permissions of the signed-in userPostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: No shared service account, no full access to other people’s mailboxes
Microsoft 365 Copilot: Works in the context of the signed-in user
Other AI add-ins: They only see what the user has opened
Rollout without a Microsoft 365 licencePostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: An MSI through group policy, the manifest from the Exchange Management Shell. A Microsoft account is possible, but not a condition
Microsoft 365 Copilot: A Copilot licence per user, on top of the Microsoft 365 licence
Other AI add-ins: The approval works on-premises too, but the account sits with the provider
Interface in nine languagesPostgate AIMicrosoft 365 CopilotOther AI add-ins
Postgate AI: German, English, Spanish, French, Italian, Portuguese, Japanese, Chinese and Korean, each matching the language of Outlook
Microsoft 365 Copilot: Multilingual
Other AI add-ins: Depends on the provider
As of September 2026. What we say about Microsoft 365 Copilot comes from Microsoft’s own documentation, which requires a mailbox in Exchange Online, and from the interest survey the Exchange Server team started in October 2025 about Copilot with mailboxes on your own hardware. What we say about other AI add-ins describes the Office add-in model, in which a task pane starts on the open item. We compare features and not providers. If your mailbox sits in Exchange Online, Copilot serves you well.
You decide which model reads your mail
The model is a setting and not something we lay down for you. Five kinds of provider are available, plus any OpenAI-compatible endpoint. If nothing is allowed to leave the building, take a model in your own network.
| Provider | Models (a selection) | Where the model runs | Available in |
|---|---|---|---|
| Anthropic | Claude Opus, Sonnet, Haiku | Anthropic cloud | hosted and self-hosted |
| OpenAI-compatible | GPT models or any endpoint of your own (vLLM, LM Studio, Azure OpenAI) | Provider cloud or your server | hosted and self-hosted |
| Mistral AI | Mistral Large, Medium, Small | Mistral cloud (EU) | hosted and self-hosted |
| OpenRouter | Claude, GPT, Gemini, DeepSeek, Qwen, Grok, Kimi and GLM, all through one key | Provider cloud | hosted and self-hosted |
| Ollama | Qwen, Gemma, Mistral and other open models | Your own server, with no API key | self-hosted only |
Anthropic
Claude Opus, Sonnet, Haiku
Where the model runs: Anthropic cloud
Available in: hosted and self-hosted
OpenAI-compatible
GPT models or any endpoint of your own (vLLM, LM Studio, Azure OpenAI)
Where the model runs: Provider cloud or your server
Available in: hosted and self-hosted
Mistral AI
Mistral Large, Medium, Small
Where the model runs: Mistral cloud (EU)
Available in: hosted and self-hosted
OpenRouter
Claude, GPT, Gemini, DeepSeek, Qwen, Grok, Kimi and GLM, all through one key
Where the model runs: Provider cloud
Available in: hosted and self-hosted
Ollama
Qwen, Gemma, Mistral and other open models
Where the model runs: Your own server, with no API key
Available in: self-hosted only
Ollama and endpoints of your own that speak the OpenAI protocol exist only in the self-hosted licence. The model server stands in your network, and our hosted environment cannot reach it at all. So mailbox and model both stay with you, and the assistant works even without internet access.
Up and running in four steps
Every step uses the tools your administrators already work with.
- 1
Approve the add-in
The Exchange administrator loads the manifest as an organisation add-in from the Exchange Management Shell and enables it for the users who need it. That covers OWA, Outlook for Windows and Outlook for Mac.
- 2
Roll out the COM add-in
On Windows the MSI package follows through group policy. The address of the task pane and the sign-in settings are handed over on the command line. After that, nothing has to be filled in on the device itself.
- 3
Sign in
Anyone with a Microsoft account signs in through Entra and stays signed in. Without a Microsoft account, a one-time code from the portal is enough. It is valid for 24 hours.
- 4
Choose the model
In the portal you set which provider and which model applies to your tenant. If you run it yourself, this is also where you enter the address of your own model server.
Frequently asked questions
Do I need Microsoft 365 or a Copilot licence?
No. The add-in works over EWS against your own Exchange Server. A Microsoft account makes signing in easier, but it is not required. Anyone without one signs in with a one-time code from the portal.
Why does Microsoft 365 Copilot not work for us?
Microsoft 365 Copilot requires the mailbox to sit in Exchange Online. For mailboxes on an Exchange Server of your own, it is not available so far. In October 2025 the Exchange team only started an interest survey on the subject. That is exactly the gap our add-in closes.
Does the add-in run in the new Outlook for Windows?
No. The new Outlook cannot connect accounts on an Exchange Server of your own, so it is not an option for our audience anyway. What we cover is classic Outlook for Windows, Outlook for Mac and Outlook in the browser (OWA).
What is the difference between the COM add-in and the web add-in?
The web add-in is approved centrally through a manifest and runs on Mac, in the browser and on Windows. Its task pane hangs off the open item. The COM add-in exists for Windows only, it arrives as an MSI and it adds a tab in the ribbon and a sidebar that stays open in every view.
Can the assistant see other people’s mailboxes?
Only the ones you are allowed to see anyway. Access runs with the permissions of the signed-in user. There is no shared account with full access to other people’s mailboxes.
Do our emails leave the building?
You decide that with your choice of model. In the hosted edition, the relevant excerpt goes to the model provider you picked. If you run it yourself with Ollama or with your own OpenAI-compatible endpoint, mailbox and model stay in your network. The assistant then works even without internet access.
Which languages does the interface come in?
Nine: German, English, Spanish, French, Italian, Portuguese, Japanese, Chinese and Korean. The task pane follows the language of Outlook, so every user sees their own.
How does the add-in reach hundreds of desks?
The web add-in needs no distribution at all, the administrator enables it once, centrally. The COM add-in arrives as an MSI package through group policy. All settings are handed over on the command line and land in the registry.
Assistant in Outlook, mailbox on your own server
Try it for 14 days, no credit card.