Microsoft Graph and EWS Managed API compatibility

Current package gaps are different from Graph gaps

Contacts, tasks, inbox rules and out-of-office settings are not in the current package. Microsoft Graph already has APIs for contacts ↗, tasks ↗, inbox message rules ↗ and automatic replies ↗. These are implementation and validation gaps in Sunsetless and will be supported after implementation and testing.

MarkAllItemsAsRead is also not in the current package. Graph v1.0 lets an app update a message's isRead value one message at a time ↗; the bulk folder action ↗ is currently beta, which Microsoft says is not supported for production. We will implement the production-supported route and document any behavior difference.

For in-place archive mailboxes, Microsoft's Outlook mail API overview ↗ says those mailboxes are not supported. Microsoft separately documents mailbox import/export APIs for archive data ↗; that is a narrower workflow than general Outlook mail access, so check whether it matches your EWS calls.

Known differences to test

• Folder listings and hierarchy sync from the mailbox root show folders of all kinds with the optional MailboxFolder.Read.All permission; without it, mail folders only. Listings under Calendar, Contacts and Tasks always work.
• Folders created through Sunsetless EWS get the class IPF.Note, like folders Outlook creates. EWS leaves it empty when the application sets none.
• Opening another mailbox through a FolderId follows the app's Graph permissions, not the impersonated user's delegate rights. One setting makes Sunsetless EWS refuse it the way EWS does.
• A SyncState saved from real EWS cannot be continued: after the switch, your app runs one full sync.
• In calendar, contacts and tasks folders, SyncFolderItems keeps a snapshot in the SyncState (about 40 bytes per item) and reads the folder on each call, because Graph v1.0 has no delta for them.
• Notifications show net changes between polls: an item created and deleted between checks produces no event, and a hard delete arrives as a delete where Exchange reports a move to Recoverable Items. Subscriptions live in your application process: resuming one from a watermark returns ErrorInvalidWatermark, as with an expired EWS subscription, so the app subscribes again and catches up through SyncFolderItems.
• Some meeting changes cannot honor SendToNone because Graph always notifies attendees; the library returns a clear error.
• Other people's free/busy comes at FreeBusy level (times, no subjects), like Exchange's default sharing.
• Out-of-office: AllowExternalOof always reads "All" (an admin setting Graph does not expose), and the reply language is not kept.
• Inbox rules: conditions and actions Graph lacks (WithinDateRange, FromConnectedAccounts, ItemClasses, MessageClassifications, SendSMSAlertToRecipients, ServerReplyWithMessage) are refused with ErrorInboxRulesValidationError.
• Moving and copying contacts, tasks and calendar items uses Graph mailbox export and import (optional MailboxItem.ImportExport.All permission); without it, these calls return a clear error. System contact folders such as Recipient Cache are not visible.
• Tasks run on Microsoft To Do. Size, PercentComplete, work and billing fields are read through the mailbox API (optional MailboxItem.Read.All permission). PercentComplete can be written only as 0 or 100, and Sensitivity, work, billing and extended properties cannot be written: a clear error instead of silent loss.
• FindPeople: each contact is its own persona (Graph does not show Exchange's persona links), and persona IDs are the library's own stable IDs.
• Search folders: the change key changes when the criteria change; EWS keeps it.
• User photos: Graph scales the photo to the requested size; EWS returned the stored size. SetUserPhoto works with ProfilePhoto.ReadWrite.All, although Exchange Online refuses it for app-only access.
• Delegates: Graph knows only the calendar part of delegation, so delegate permissions to other folders return a clear error.
• User configuration: only CategoryList and WorkHours; an application's own configuration objects return a clear error.
• MarkAsJunk moves the item but leaves the blocked and safe senders lists unchanged: Microsoft Graph v1.0 has no API for them. A call that only changes the lists fails with a clear error.
• Sorting by subject: Graph ignores RE: and FW: prefixes, EWS does not.
• Contact groups are read-only: creating, changing or deleting one returns a clear error, because Graph cannot delete them.
• Retention tags: after a change through the library, RetentionDate appears only once Exchange computes it, because Graph does not know tag periods.
• Enhanced location: attendees get the invitation from the first save, without the location annotation and source, which the library writes in a second save.
• Properties Exchange Online leaves empty for applications (Mentions, Hashtags, Likers and similar) are empty here too; NormalizedBody returns an error.
• Task attachments: Microsoft To Do keeps files only, so attaching an item to a task returns a clear error.
• Posts are created from a message saved through Graph: they are larger, and the folder briefly shows that message too.
• Series invitations: AppointmentSequenceNumber is one higher, because Graph saves a meeting before sending it.
• Responses to meetings refer to the invitation in InReplyTo and References, where EWS refers to the calendar item.
• Meeting time suggestions are rated like Exchange does; equally good slots outside working hours may come in a different order.
• Operations without a Graph equivalent return the same error code that Exchange Online gives applications, with the reason from the library.