Incorrect delta result from GetAsDeltaGetResponse on mail folder

Describe the bug

I am using Delta handling against a mail folder and have found that consistently if older messages are added to the folder the delta query will return them twice in the result

Expected behavior

Expectation is that the delta call would only return a message once

How to reproduce

Reproduction-
(dates of the emails added to highlight the problem, not specifically needed to reproduce)

Folder with 1 email (14/01/2026)
Client.Me().MailFolders().ByMailFolderId(folderId).Messages().Delta().GetAsDeltaGetResponse() against the folder

• returns 1 email plus the delta link for use later

move 2 more recent (20/01/2026 ) emails into the folder
Client.Me().MailFolders().ByMailFolderId(folderId).Messages().Delta().WithUrl(deltaLink).GetAsDeltaGetResponse()

• returns 2 emails and new delta link

move 2 older emails (09/01/2026, 22/12/2025) into the folder
Client.Me().MailFolders().ByMailFolderId(folderId).Messages().Delta().WithUrl(newdeltaLink).GetAsDeltaGetResponse()

• returns 4 emails (2x each of the emails it should be returning) and new delta link

SDK Version

v1.93.0

Latest version known to work for scenario above?

N/A

Known Workarounds

N/A

Debug output

No response

Configuration

No response

Other information

No response

Start with the Delta().GetAsDeltaGetResponse() and Delta().WithUrl(deltaLink).GetAsDeltaGetResponse() calls described in the reproduction, and trace how the returned items and delta links are handled. Reproduce the sequence of adding newer and then older messages to a mail folder. Done means each changed message appears once in the delta response with a usable new delta link.