Why are Microsoft Bookings emails going to junk or bouncing?

How to tell which problem you have#

Not every delivery failure is the same. Check what's happening before you change anything:

Microsoft states the risk directly in its Teams admin documentation: the default domain "might cause problems when sending meeting invites to external recipients", and invites may be "flagged as spam and moved to the recipient's junk folder".

Fix 1: move the booking mailbox to your own domain#

There's no setting inside Bookings for this. The Bookings FAQ says sender addresses "are controlled and managed at the Microsoft 365 settings level". A Microsoft 365 admin has to do it.

For an existing booking page, Microsoft's documented command (Exchange Online PowerShell) is:

Set-Mailbox -Identity business@contoso.onmicrosoft.com -WindowsEmailAddress business@contoso.com -EmailAddresses business@contoso.com

Replace the addresses with your booking mailbox and your verified domain. Passing a single value to -EmailAddresses replaces the mailbox's address list, so plan for that before you run it. After the change, open the public booking link again and do a test booking. Community reports differ on whether the public URL changes or simply redirects, so update any links you publish if it changed.

For future booking pages, set the default domain once so new pages never start on onmicrosoft.com:

Set-OwaMailboxPolicy -Identity OwaMailboxPolicy-Default -BookingsMailboxDomain "contoso.com"

Microsoft notes this "will not impact shared booking pages that have already been created". The full walk-through, including per-user policies, is on the change the sender email page.

Fix 2: check SPF, DKIM and DMARC for that domain#

Moving to your domain only helps if the domain authenticates Microsoft 365 mail:

• SPF: your domain's SPF TXT record must include Microsoft 365 as a sending source.
• DKIM: turn on DKIM signing for the custom domain in Microsoft 365.
• DMARC: publish a DMARC record so receivers can check that the From domain aligns with SPF or DKIM.

Microsoft describes these standards as "interdependent building blocks that work together", so set up all three rather than one. If you already send normal staff email from the domain without junk problems, these are probably in place.

Fix 3: check your own mail flow rules#

Several bounce threads traced back to the organisation's own Exchange transport rules, which blocked or modified mail from the onmicrosoft.com sender. Ask your admin to:

1. Run a message trace in the Exchange admin center for a recent confirmation to a failing recipient.
2. Look for a transport rule, connector or third-party mail gateway that rejects, rewrites or quarantines the booking mailbox's messages.
3. Read the bounce text. A 550 5.7.1 from the recipient's server points at sender authentication. A rejection from your own gateway points at a rule.

What you can't change#

As of September 2026:

• The From address can't be set per service or per page in the Bookings UI. The "Send customer replies to" field on Business information only changes where replies go.
• The email template itself isn't editable. You can add text in "Additional information for Email Confirmation" on each service, but not change the subject or layout. See customizing the confirmation email.
• Microsoft doesn't document any deliverability monitoring for Bookings emails. Message trace in Exchange is the only built-in tool.

If you'd like the booking page URL itself to sit on your domain, that's a different question, covered in using your own domain for Bookings.