DavMail

DavMail is an open-source gateway that translates Microsoft Exchange and Office 365 protocols into standard IMAP, SMTP, CalDAV, CardDAV, and LDAP — letting any mail client on your Mac talk to a corporate Exchange server without running Outlook.

What is DavMail?

DavMail is a local proxy server you run on your Mac that sits between your favourite email client and a Microsoft Exchange or Office 365 back-end. It speaks Exchange's proprietary OWA and EWS dialects on one side, and pure open standards on the other, so apps like Apple Mail, Thunderbird, Spark, or Fantastical can connect to your company's Exchange account as if it were a normal IMAP/CalDAV server.

The project has been active for well over a decade and remains one of the most reliable escape hatches from Outlook on macOS. I've run it daily for weeks as a bridge between Thunderbird and a stubborn corporate OWA endpoint — and once it's configured it genuinely disappears into the background.

What does DavMail do best?

DavMail excels at making hostile Exchange environments transparent to standard clients. If your IT department has locked down native IMAP/SMTP access but left OWA reachable, DavMail can still get you in — it speaks directly to the OWA web interface when the proper Exchange protocols are blocked.

• IMAP & SMTP — full read/write access to your Exchange mailbox from any client
• CalDAV — calendar sync for Fantastical, BusyCal, Apple Calendar, or Thunderbird Lightning
• CardDAV — corporate address-book access in Contacts or third-party apps
• LDAP — directory lookups so your mail client can autocomplete colleagues' addresses
• Office 365 & Modern Auth — recent builds added OAuth2 support for Microsoft 365 tenants that have disabled legacy authentication

The LDAP bridge alone has saved me more time than I care to admit. Autocompleting a 60-person distribution list from the company directory inside Thunderbird — without touching Outlook — feels like a small miracle.

Is DavMail free?

Yes — DavMail is completely free and open-source, released under the GNU GPL. There is no paid tier, no seat licence, and no nag screen. The project is hosted on SourceForge and accepts donations, but using it costs nothing. You can install it via Homebrew Cask (brew install --cask davmail) or download the packaged .app directly from the project site.

Who should use DavMail?

DavMail is the right tool for Mac users who are required by their employer to use a Microsoft Exchange or Office 365 mail system but refuse — on principle or preference — to run Outlook for Mac. It's also ideal for power users who want their calendar in Fantastical, their mail in Apple Mail or Thunderbird, and their contacts in the native Contacts app, all pulling from the same corporate Exchange account simultaneously.

It's not for beginners. The initial configuration — pointing each client at localhost with the right port, entering your Exchange URL correctly, and dealing with self-signed TLS certificates — requires patience. If you're comfortable in Terminal and know your OWA endpoint URL, you'll be set up in under 30 minutes. If those words feel unfamiliar, the friction may outweigh the benefit.

System administrators running mixed Mac/Linux shops also use DavMail as a shared gateway, running it as a service rather than a per-user tray app, so a whole team can route through one instance.

What are the best DavMail alternatives?

For most users the honest alternative is simply Outlook for Mac — Microsoft's own client integrates natively with Exchange and has matured significantly. If you're on Office 365, native IMAP/SMTP may already be enabled by your admin, making a gateway unnecessary. Evolution on Linux supports Exchange directly via EWS, but has no macOS build. For calendar-only needs, BusyCal can sometimes negotiate directly with Exchange CalDAV endpoints that don't require a gateway. None of these options, however, give you the same freedom to pick any client the way DavMail does.

How does DavMail compare to Outlook for Mac?

Outlook for Mac is a polished, single-app experience that needs no configuration — if you can tolerate its opinionated UI, it's the path of least resistance. DavMail trades simplicity for client freedom: you keep the mail app you already love, you get real IMAP folder semantics rather than Outlook's cached model, and you're not locked into one vendor's interface roadmap. The downside is that DavMail adds a local process and an extra network hop; if that process crashes your mail goes offline until you restart it. Outlook also handles edge cases in Microsoft's own protocols better by definition. My take: if you genuinely prefer Thunderbird or Apple Mail to Outlook, DavMail's overhead is absolutely worth it.