DavMail 7.0.0 Pivots to Microsoft Graph With Delta Sync, Drops Legacy Settings

DavMail, the open-source Java gateway that lets people use their favorite mail and calendar apps instead of Outlook while still connecting to Exchange and Office 365, has released version 7.0.0 with a significant shift in how it talks to Microsoft's servers. The new version turns on a more efficient syncing method by default, removes a setting that some administrators have relied on, and tightens security on Linux systems by locking down its token file.

The core job DavMail does is translation. Exchange and Office 365 speak their own language—Exchange Web Services, or EWS, for the older systems, and Microsoft Graph for the newer ones. But most mail clients, calendar apps, and contact managers speak open standards: IMAP for mail, SMTP for sending, CalDAV for calendars, CardDAV for contacts, and LDAP for directory lookups. DavMail sits in the middle and converts requests from one side to the other. For anyone who wants to escape Outlook's weight but can't escape their company's Exchange mailbox, it's been a lifeline.

Version 7.0.0 is heavily weighted toward Graph. Of seventy changelog entries tagged with Graph improvements, only eighteen touch EWS. The biggest single change is folder delta sync. Until now, every time a mail client checked a folder, DavMail would ask Graph for the entire contents and compare it to what it had seen before. With delta sync enabled by default, DavMail instead asks Graph only what changed since the last check and keeps a cached copy of the folder locally. The result is less data moving across the network and faster checks. The feature was available as an option before—davmail.graph.deltaSync—but now it's on automatically.

The release also handles some of the friction that comes with talking to Microsoft's servers. When Microsoft throttles a client that's making too many requests, it sends back a Retry-After header telling the client how long to wait. DavMail now caps how many times it will retry and can handle a malformed Retry-After header that doesn't follow the standard format. Messages appended over IMAP now preserve their original date, headers, threading, and read status. Meeting responses can now target a single occurrence of a recurring event instead of the whole series.

For contact management, DavMail now returns distribution lists as contact groups that mail clients can display. The project has disabled this feature for Thunderbird, noting it's not yet supported there. A new read-only mode for calendars—davmail.caldavReadonly=true—lets clients view shared calendars without accidentally writing changes back to Exchange.

But there are breaking changes administrators need to know about before upgrading. The davmail.caldavImpersonate setting is gone. DavMail now handles impersonation of shared mailboxes automatically when sending meeting responses from a shared calendar, which simplifies configuration but removes a lever some admins had been using. More importantly, Graph users will need to ensure their Microsoft tenant approves a new permission scope: Calendars.ReadWrite.Shared, which DavMail now requests to reach shared folders. If an admin's tenant restricts which permissions apps can request, they need to explicitly approve this scope before upgrading. Token validation will fail outright if the Mail.ReadWrite permission is missing. The switch from EWS to Graph also forces a fresh sign-in—users won't be able to reuse their old tokens. For organizations with strict permission policies, this is the moment to check the approval list and make sure the new scope is there before anyone upgrades.