Technology · head to head
Microsoft Outlook vs Restate
Microsoft Outlook
Technology
Microsoft's email and calendar client, in the middle of a transition from the classic Windows application to a web-based replacement.
- From
- Free
- Free plan
- Yes
Restate
Developer Tools
Durable execution engine in Rust with a free tier and low-latency workflows
- From
- Free
- Free plan
- Yes
The short version
- Each has a real cost: Microsoft Outlook microsoft is replacing the classic Win32 client with the new web-based Outlook, and the new one runs only web add-ins, not COM add-ins, so any line-of-business integration for CRM, dictation, document management or telephony must be rewritten or the desktop stays on classic until its support window closes.; Restate the runtime is under a Business Source Licence rather than an open source licence, so building a competing managed offering on it is prohibited and some procurement functions will reject it on licence grounds alone.
- They diverge on capability: Microsoft Outlook covers Exchange calendar integration, Restate covers Durable execution.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which Microsoft Outlook and Restate actually diverge.
| Attribute | Microsoft Outlook | Restate |
|---|---|---|
| Pricing model | freemium | Per month by durable action count |
| Platforms | Web | Linux, macOS, Web |
| Category | Technology | Developer Tools |
Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).
What each one covers
Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.
Only in Microsoft Outlook
- Exchange calendar integration
- Delegate access
- Shared mailboxes
- Rules and Quick Steps
- Retention, hold and eDiscovery
- Sensitivity labels and encryption
- Add-in platform
- Offline cached mode
Only in Restate
- Durable execution
- Virtual objects
- Single binary runtime
- Multi-language SDKs
- Workflows and sagas
- Restate Cloud
What people use each for
The jobs each tool is most often brought in to do.
Microsoft Outlook
- Organisations on Exchange Online or Exchange Server where free/busy scheduling and room booking across everyone is a daily requirementnot Restate
- Executive assistants managing someone else's calendar and mailbox through delegate access, which no IMAP client supports properlynot Restate
- Regulated environments that need retention policies, legal hold and eDiscovery applied to mail centrally rather than per usernot Restate
- Teams handling shared inboxes such as support or accounts, where permissions and tracking matter more than the mail client itselfnot Restate
Restate
- Payment or order flows where a crash between two external API calls must not double-charge or lose the ordernot Microsoft Outlook
- AI agent loops that call tools over minutes or hours and must survive a deployment mid-runnot Microsoft Outlook
- Replacing hand-rolled retry, idempotency key and outbox code across a set of microservicesnot Microsoft Outlook
- A small team that wants durable workflows without operating a Temporal cluster and its databasenot Microsoft Outlook
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
Microsoft Outlook
- Microsoft is replacing the classic Win32 client with the new web-based Outlook, and the new one runs only web add-ins, not COM add-ins, so any line-of-business integration for CRM, dictation, document management or telephony must be rewritten or the desktop stays on classic until its support window closes.
- The new client's handling of non-Microsoft accounts synchronises mail through Microsoft's cloud rather than connecting from the machine to the provider, which several organisations' data residency and handling policies do not allow, and it is not an optional behaviour.
- PST and OST files are a single-file, corruptible and effectively unshareable store, and the new client's reduced PST support means years of personal archives sitting in those files need an explicit migration plan rather than carrying forward.
- Large mailboxes turn software problems into administration ones: search index rebuilds, OST files of tens of gigabytes and the mailbox quotas of whichever plan was bought, and the usual fix is archiving policy rather than anything a user can do.
- Against IMAP or Gmail you lose most of what justifies it, including free/busy lookup, room booking, delegate access, and retention and compliance policies, because those are Exchange server features rather than client features.
- The five or six products sharing the Outlook name have materially different feature sets, so internal documentation, training and support procedures must be written per platform and a user moving between desktop, web and mobile finds the same task done differently in each.
Restate
- The runtime is under a Business Source Licence rather than an open source licence, so building a competing managed offering on it is prohibited and some procurement functions will reject it on licence grounds alone.
- Restate Cloud jumps from a free fifty thousand actions straight to 300 US dollars a month for twenty million, so a workload sitting at a few hundred thousand actions pays enterprise-shaped money for hobby-shaped volume.
- It is a young project against Temporal’s established base, so hiring engineers who already know it is unrealistic and the answer to most questions is in the docs rather than on Stack Overflow.
- The programming model requires structuring code around durable handlers and virtual objects, which is a genuine rewrite for existing services rather than a library you add.
- The single-binary simplicity that makes small deployments cheap also means fewer operational knobs at very large scale than a system designed as separable components.
Pricing, plan by plan
Microsoft Outlook
Free- Outlook (Free)Free
- 15 GB mailbox storage
- 5 GB cloud storage
- Web and mobile Office app access
- Microsoft 365 Basic$1.99/month
- 100 GB mailbox storage
- 100 GB cloud storage
- Ad-free experience
- Microsoft 365 Personal$9.99/month
- 1 TB cloud storage
- Desktop Office apps (Word, Excel, PowerPoint, Outlook, OneNote)
- Copilot with high usage limits
- Microsoft 365 Family$12.99/month
- 1-6 users
- Up to 6 TB total cloud storage (1 TB per person)
- Same apps and features as Personal
Restate
Free- FreeFree
- Fifty thousand durable actions per month
- No credit card required
- Community support
- Starter$300/month
- Twenty million actions per month
- Two hundred actions per second, bursting to one thousand
- Twenty GB storage
- Pro$1000/month
- Fifty million actions per month
- Five hundred actions per second, bursting to two thousand
- Fifty GB storage
- Enterprise$undefined/year
- Negotiated volume
- Twenty-four seven P0 support
- 99.99 per cent SLA
Which should you pick?
Choose Microsoft Outlook if
- You need exchange calendar integration.
- You want to start without paying.
- You also want delegate access.
Choose Restate if
- You need durable execution.
- You want to start without paying.
- You work on Linux, macOS, Web.
- You also want virtual objects.
Questions people ask
- Is Microsoft Outlook or Restate better?
- Neither clearly leads. Microsoft Outlook starts at Free and Restate at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Microsoft Outlook or Restate?
- Microsoft Outlook starts at Free and Restate at Free.
- Does Microsoft Outlook or Restate run on more platforms?
- Microsoft Outlook runs on Web. Restate runs on Linux, macOS, Web.
- Can I use Microsoft Outlook for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Microsoft Outlook best used for?
- Microsoft Outlook is most often used for organisations on exchange online or exchange server where free/busy scheduling and room booking across everyone is a daily requirement, executive assistants managing someone else's calendar and mailbox through delegate access, which no imap client supports properly, regulated environments that need retention policies, legal hold and ediscovery applied to mail centrally rather than per user, teams handling shared inboxes such as support or accounts, where permissions and tracking matter more than the mail client itself. Of those, organisations on exchange online or exchange server where free/busy scheduling and room booking across everyone is a daily requirement and executive assistants managing someone else's calendar and mailbox through delegate access, which no imap client supports properly are not what Restate is typically brought in for.
- What can Microsoft Outlook do that Restate cannot?
- Microsoft Outlook covers Exchange calendar integration, Delegate access, Shared mailboxes, Rules and Quick Steps. Restate covers Durable execution, Virtual objects, Single binary runtime, Multi-language SDKs.
Answered from the vendors’ own pages
Microsoft Outlook: What is the difference between classic Outlook and the new Outlook for Windows?
Classic is the long-standing Win32 application shipped with Microsoft 365 and Office LTSC. The new Outlook is a web-based client that replaced Windows Mail and Calendar. The most consequential difference is add-ins: the new client supports only web add-ins, not COM add-ins.
Restate: Is Restate open source?
The SDKs are MIT. The runtime is under a Business Source Licence, which permits self-hosting but not offering it as a competing service.
Microsoft Outlook: How long will classic Outlook be supported?
Microsoft has stated support through at least 2029. That is a planning window rather than a reprieve, and organisations with COM add-in dependencies should be scoping the replacement work now.
Restate: How does it compare with Temporal?
Same problem, different shape: one Rust binary with embedded storage instead of a server plus database plus workers, and lower per-step latency.
Microsoft Outlook: Can I use Outlook with Gmail or another IMAP provider?
Yes, but with reduced capability. You lose free/busy lookup, room booking, delegate access and server-side compliance policies, because those come from Exchange rather than from the client.
Restate: Is there a free tier?
Yes, fifty thousand durable actions a month on Restate Cloud with no card required.
Microsoft Outlook: Is Outlook free?
Outlook on the web and the mobile apps are free with a Microsoft account, and the new Outlook for Windows is included with Windows 11. The classic desktop application requires a Microsoft 365 subscription or an Office perpetual licence.
Restate: Which languages are supported?
TypeScript, Java, Kotlin, Go, Python and Rust.
Microsoft Outlook: Will my COM add-ins work in the new Outlook?
No. The new client supports only the cross-platform web add-in model. Vendors must publish a web add-in, and where they have not, the choice is to stay on classic Outlook or replace the integration.
Related pages
More on Microsoft Outlook
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