Mail flow and message trace, SPF/DKIM/DMARC, anti-spam, NDRs, mailbox and recipient management, retention and Exchange Online PowerShell.
Run a message trace in the Exchange admin center or with Get-MessageTraceV2, read the delivery status and events, and pull older data from downloadable reports.
Read the X-Forefront-Antispam-Report header (CAT, SFV, BCL, compauth) to see why a good message was junked, then fix it the supported way: submissions, Tenant Allow/Block List, sender authentication, not bypass rules.
A six-stage MS-102 study plan built on the official Microsoft Learn paths, with extra Exchange Online practice, lab ideas and what the November 2026 retirement of the exam means for you.
Purview retention policies vs retention labels vs Exchange MRM tags vs litigation hold: what each does, what wins in a conflict, licensing, how to set them up and how to prove a mailbox is really on hold.
Exchange Web Services is being disabled in Exchange Online from October 2026. What changes, how EwsEnabled and EwsAllowedAppIDs work, how to find what still uses EWS and how to buy time safely.
Why Exchange Online rejects mail with 550 5.4.1 at the perimeter, how Directory-Based Edge Blocking and the accepted domain type cause it, and how to fix each common cause.
Get SPF, DKIM and DMARC right, trace messages that never arrive, and fix the NDRs and relay problems admins see most.
Start the series 6 partsThe recipient and retention decisions every Microsoft 365 admin makes — groups vs shared mailboxes, rooms, archives, holds — plus the Outlook connectivity issues behind most mailbox tickets.
Start the seriesSymptom, root cause, fix — and how to verify it.
Step-by-step setup guides with the exact settings.
How a feature really works, and how to choose.
Study plans for MD-102, SC-300, SC-200 and MS-102.
Tell me which error or task you'd like covered next — new guides come from readers' questions.
