Fix Exchange Messages Moving to Junk with CreateRecipientItems.40 Error
Question details
Exchange messages are being intermittently routed to the Junk Email folder instead of the Inbox, accompanied by a specific message trace error.
- Product
- Microsoft Exchange
- Device & OS
- not provided
- Scenario
- Tracking email delivery using message trace and identifying backend routing failures.
- Observed behavior
- Message trace reports the error UserMailbox.Forwardable.Resolver.CreateRecipientItems.40 as emails are unexpectedly delivered to the Junk folder.
Ensure you have administrator access to the Microsoft 365 Defender portal and Microsoft admin center before modifying organizational anti-spam policies.
Review Microsoft 365 Anti-Spam Policies and Inbox Rules
Check your organization's threat policies and individual mailbox rules to ensure legitimate emails are not being incorrectly flagged as spam.
Often, emails end up in the Junk folder due to overly strict global anti-spam configurations or conflicting user-level rules. Verifying both administrative policies and local Outlook settings helps isolate the cause.
Log in to the Microsoft 365 Defender portal using your administrator credentials.
In the left navigation menu, go to Email & Collaboration, select Policies & Rules, then click on Threat policies, and finally choose Anti-spam.
Open your active anti-spam policies and check the 'Allowed and blocked senders and domains' list to ensure the affected sender is not inadvertently blocked.
Have the affected user check their personal Outlook inbox rules and Blocked Senders list to ensure local settings are not overriding global delivery rules.
Contact Microsoft 365 Support for Backend Investigation
Escalate the issue to Microsoft Support, as the CreateRecipientItems.40 error often indicates a backend Exchange resolution problem.
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Frequently Asked Questions
What does the CreateRecipientItems.40 error mean in Exchange message trace?
This specific error generally indicates a mailbox resolution or forwarding rule complication on the backend of Microsoft Exchange, causing standard inbox routing to fail and defaulting the message to the Junk Email folder.
Can user-created Outlook rules bypass organizational spam filters?
Yes. If a user configures aggressive local inbox rules or manually adds a domain to their personal Blocked Senders list in Outlook, it can force legitimate messages into the Junk folder regardless of broader administrative policies.
How do I whitelist a sender in Microsoft 365 Defender?
In the Defender portal, navigate to Email & Collaboration > Policies & Rules > Threat policies > Anti-spam. Edit the 'Anti-spam inbound policy' and modify the 'Allowed and blocked senders and domains' section to whitelist the trusted sender.
Why are emails with attachments frequently moving to the Junk folder?
Emails containing certain file types, notably executables, scripts, or macro-enabled documents, trigger Microsoft 365's aggressive spam and malware defense mechanisms. Reviewing your organization's Safe Attachments policy can help adjust these sensitivity levels.
