Exchange Online Toolkit — oeltayeb.com
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Mail-flow checklists for message trace, SPF/DKIM/DMARC, the NDRs admins meet most often, compromised-mailbox investigation and anti-spam tuning, plus the SMTP AUTH relay reference for printers and apps.

Every file in this folder is a self-contained HTML page: open it in any browser and use Print / save as PDF.
Each resource was derived from an article on https://www.oeltayeb.com and links back to it — read the article when you need
the reasoning behind a step.

Contents
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- exchange-online-message-trace-troubleshooting-checklist.html — Checklist: Email never arrived? Using message trace in Exchange Online to find out why
    source: https://www.oeltayeb.com/articles/exchange-online-message-trace-troubleshooting.html
- spf-dkim-dmarc-setup-checklist.html — Checklist: SPF/DKIM/DMARC setup checklist
    source: https://www.oeltayeb.com/articles/spf-dkim-dmarc-microsoft-365-custom-domain.html
- ndr-550-5-7-520-external-forwarding-blocked-checklist.html — Checklist: NDR 550 5.7.520: fixing “Your organization does not allow external forwarding”
    source: https://www.oeltayeb.com/articles/ndr-550-5-7-520-external-forwarding-blocked.html
- ndr-550-5-4-1-recipient-address-rejected-access-denied-checklist.html — Checklist: NDR 550 5.4.1 “Recipient address rejected: Access denied”: Directory-Based Edge Blocking
    source: https://www.oeltayeb.com/articles/ndr-550-5-4-1-recipient-address-rejected-access-denied.html
- compromised-mailbox-investigation-checklist.html — Checklist: Compromised mailbox investigation checklist
    source: https://www.oeltayeb.com/articles/investigate-compromised-mailbox-exchange-online-inbox-rules-audit.html
- legitimate-email-going-to-junk-tuning-anti-spam-exchange-online-checklist.html — Checklist: Legitimate email landing in Junk: how EOP decides and the right way to fix it
    source: https://www.oeltayeb.com/articles/legitimate-email-going-to-junk-tuning-anti-spam-exchange-online.html
- smtp-auth-relay-printers-apps-error-5-7-57-reference.html — Reference: Printers and apps can't send via Microsoft 365: SMTP AUTH, relay connectors and 5.7.57
    source: https://www.oeltayeb.com/articles/smtp-auth-relay-printers-apps-error-5-7-57.html

Related PowerShell scripts (read-only by default, MIT licence)
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- Get-EXOExternalForwardingReport.ps1: Finds mail leaving the tenant through mailbox forwarding or inbox rules, and optionally removes it.
- Get-EXOMailboxPermissionsReport.ps1: Audits delegated mailbox access: FullAccess, SendAs and SendOnBehalf grants across Exchange Online mailboxes.
- Get-EXOMailboxSizeReport.ps1: Reports mailbox and archive size, item counts and quota usage for Exchange Online mailboxes.
  https://github.com/omer-eltayeb/M365-Intune-Admin-Scripts

Licence
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Free to use and share within your organisation; please link to www.oeltayeb.com when you redistribute.

© Omer Eltayeb · https://www.oeltayeb.com · Shared free for the Microsoft community. Verify settings in a test tenant first.
