Product · Email & calendar
Business email and calendar,
on infrastructure you choose.
Mailboxes, shared mailboxes, calendars, contacts and resource booking, delivered through an Outlook-style web interface — the part of Microsoft 365 and Google Workspace most organizations depend on every hour of the day.
Project status Email and calendar are planned for the core-services phase. Nothing on this page is available yet; mail-server candidates are under evaluation.
What it replaces
Exchange Online, Outlook on the web, and Gmail with Google Calendar and Contacts, for day-to-day business use.
Email is the workload that cannot go down. It carries contracts, invoices, password resets and customer conversations, and it is the first thing a business notices when it stops. It is also where expectations are highest: people have used Outlook or Gmail for years and judge any alternative against them within minutes.
Office Unbound’s mail and calendar service is designed around both facts. The server side is built on established open-source mail software rather than written from scratch, because reliable mail transport, storage and filtering are hard problems that mature projects have already solved. The work Office Unbound adds is the part users and administrators touch: a familiar, capable web client, a shared identity with every other service, and administration that sits beside files, chat and meetings instead of in a separate console.
Intended capabilities
The functionality this service is being designed to provide. Each line carries its current status; none is available yet.
- Available Available and verified in a release
- In development Being built now
- Planned In the roadmap, not yet started
- Under evaluation Being assessed; not yet selected
| Capability | What it means | Status |
|---|---|---|
| Business email hosting | Mailboxes on your own domains, with standard IMAP/SMTP access as well as the web client. | Planned |
| Multiple domains | Several domains per organization, and per customer for MSP deployments. | Planned |
| User and shared mailboxes | Personal mailboxes, plus shared mailboxes for teams such as sales@ or support@. | Planned |
| Distribution lists | Group addresses that deliver to their members, managed from the directory. | Planned |
| Aliases and forwarding | Additional addresses per user and administrator-controlled forwarding. | Planned |
| Signatures | Per-user signatures, with organization-wide templates. | Planned |
| Folders, search and rules | Folder organization, full-text search and server-side rules and filters. | Planned |
| Out-of-office replies | Scheduled automatic replies set by the user or an administrator. | Planned |
| Calendars and scheduling | Personal and shared calendars, meeting invitations and free/busy lookup. | Planned |
| Contacts and company directory | Personal address books and a directory generated from user accounts. | Planned |
| Room and resource booking | Bookable rooms and equipment with their own calendars. | Planned |
| Mailbox delegation | Send-as, send-on-behalf and calendar delegation for assistants and shared roles. | Planned |
| Retention and archiving | Retention policies and archive storage set by the administrator. | Planned |
| Mobile access | Mail, calendar and contacts on phones through standard protocols. | Planned |
| Desktop client interoperability | Use of existing desktop mail clients, subject to protocol testing. | Under evaluation |
| Administrative controls | Quotas, policies and mailbox management from the central console. | Planned |
An Outlook-like web client
Familiar, capable, and honest about what “familiar” means.
A key objective is a webmail interface that someone who has used Outlook for ten years can work in on their first day: a folder pane, a message list, a reading pane, a calendar a click away, and keyboard shortcuts that behave as expected. It should handle a large mailbox without slowing down, and it should feel like part of one product with the file, chat and meeting services rather than a separate application with a different look.
That is a design objective, and it is separate from protocol compatibility — whether the desktop Outlook application, Apple Mail, Thunderbird or a phone’s built-in mail app can connect to the server. Those depend on which protocols the selected mail server implements and how well, and they will be stated only once they are tested.
Office Unbound does not claim that Microsoft Outlook for Windows or macOS will work against its mail service. Some candidate servers implement Exchange-compatible protocols (MAPI over HTTP, Exchange ActiveSync, EWS) to varying degrees; whether the result is good enough for everyday use is exactly what evaluation has to establish. Standard IMAP, SMTP, CalDAV and CardDAV clients are the safer expectation.
Technology under evaluation
The mail server is the most consequential choice in the platform, so it is being made carefully.
- grommunio / Gromox
- A groupware server that implements Exchange protocols — MAPI over HTTP, EWS and ActiveSync — alongside IMAP, POP3, CalDAV and CardDAV. The leading candidate where Outlook desktop compatibility matters. Under evaluation
- Stalwart
- A modern mail and collaboration server written in Rust, with JMAP, IMAP, SMTP, CalDAV and CardDAV, built-in spam filtering and a smaller operational footprint. An alternative where standards-based clients are acceptable. Under evaluation
- Postfix
- Long-established mail transfer agent for routing and relay where the selected server does not handle transport itself. Under evaluation
- Rspamd
- Spam filtering with SPF, DKIM, DMARC and ARC evaluation, reputation and statistical classification. Under evaluation
- ClamAV
- Open-source antivirus scanning of attachments in transit. Under evaluation
- MailThreatZero
- An optional additional email security layer for phishing and threat filtering, where an organization wants more than the built-in filtering. Under evaluation
None of these is integrated into Office Unbound today. Selection depends on protocol coverage, operational behavior at scale, multi-tenant support and licensing — see Technology stack and licensing.
Deliverability and security
Running your own mail means owning its reputation. The service is being designed to publish and check the records receiving servers rely on — SPF, DKIM signing, DMARC policy, MTA-STS and TLS reporting — as part of adding a domain rather than as a checklist for the administrator. Inbound mail is to pass through spam and malware filtering with a quarantine that administrators can review and release.
Deliverability is never fully in a sender’s control. Large mailbox providers make their own judgements about IP addresses and domains, and a new installation has no reputation yet. Office Unbound will document what operators need — clean IP addresses, correct reverse DNS, sensible sending volumes — rather than promise inbox placement.
Coming from Exchange or Gmail
Mail, calendars and contacts are the first workloads the planned migration tooling is designed to move: messages and folders with their dates intact, calendar events including recurrences, and contacts. Gmail labels, which can place one message in several places at once, need a decision about how they become folders — the assessment is meant to surface that decision before anything moves.
Planning to move your mail?
Tell us what you run today and which workloads matter most. It shapes what is built and tested first.