Microsoft 365 emails going to spam: where to start

Separate three different problems

Keep these categories separate in your support brief. A recipient spam filter and a sender restriction can look similar from the sender’s desk but require different evidence.

Confirm which service sent it

The Outlook application can display an account without being the delivery service for every connected tool. A CRM can send through a mailbox connection or through separate infrastructure using the same visible From address.

Compare one expected mailbox message with the affected message. Record the app, sending account and message type. For an automated message, identify the platform and product, not just “Outlook”.

Ask the administrator for message trace

Microsoft’s documented starting point is the Exchange admin centre, under Mail flow and Message trace. This requires appropriate permissions. Ask the authorised mail administrator to inspect the exact sender, recipient and time range, including the time zone.

Give them the message ID or the full non-delivery report when available. Ask what the trace shows, which system accepted or rejected the message, and whether further recipient-side evidence is needed. Do not request broad administrative access merely to investigate one message.

A sending-side delivery event is useful evidence, but it should not be described as proof that an external person read the message.

If the account is restricted

Ask IT to investigate the reason, any unusual sending activity and the associated alerts before restoring sending. A compromised mailbox and an intended campaign need different responses.

Check for queued mail before resuming activity. Immediately releasing a large queue can repeat the pattern that triggered the restriction. Keep the incident evidence and any planned retest with the administrator.

Do not disable outbound protection or broadly allow-list your domain as a general deliverability fix. That can obscure the cause and affect security.

If mail reaches the recipient’s junk folder

Get the original received-message headers from a willing recipient. Use them to identify the sending route and the recorded authentication outcome. Our header explainer can help read that text, but it cannot verify the trustworthiness of a result block.

If authentication passes, compare affected recipients, message types and recent changes. A managed Microsoft 365 tenant can apply policies that differ from personal Outlook.com. Keep a controlled test in perspective.

Keep bulk campaigns separate from everyday mail

Microsoft documents limits and protections for its service and describes bulk sending as a best-effort use rather than a supported bulk-email service. Do not treat a mailbox as an unlimited sending engine.

Before moving a campaign to another route, review its purpose, recipient expectations and the destination service’s rules with the responsible administrator. Changing domains or software does not make unwanted email wanted.

Prepare a useful support handoff

Record a confirmed example, the precise time, the real sending route, the complete error if any, and what changed recently. Separate facts from guesses. The IT handoff builder creates a brief you can share through your own approved channel.

For a rejection, continue with the bounce guide. For a message accepted but apparently unseen, read delivered versus inbox.