I am not receiving all my emails

Hi @Crystal Hanlon, 

I hope you're doing well today. 

Based on the information you shared that in Classic Outlook, some emails sent to your address are not arriving, and at times senders receive an undeliverable message even though other emails are delivered successfully. 

This type of issue can happen when email delivery is affected by mailbox rules, junk filtering, synchronization problems in Outlook, a server side mail flow check that accepts some messages but rejects others or when Outlook cannot complete a stable connection to the mailbox service, which then prevents new items from downloading and updating. Since the behavior is intermittent, the issue may be related to both the Outlook application and the account’s delivery status on the mail service. 

Below is a clear and detailed guide to walk you through the steps that can restore your user’s ability to receive emails. If you don't have a permission, please contact your IT's administrator to follow this steps below:     

Option 1: If you are an end-user, please try the step below first  

1/ Refresh again the connection   

• First, open Classic Outlook, then select the Send/Receive tab and choose Work Offline once so the option is no longer selected.  
• Next, check the Outlook status bar and confirm it changes away from Working Offline and begins connecting, because Outlook will only resume syncing after it is back online. Work offline in Outlook - Microsoft Support   

2/ Recheck Send/Receive group settings and force a sync  

• Then, go to Send/Receive, open Send/Receive Groups, and select Define Send/Receive Groups so you can confirm your account is included in the active group and that an automatic schedule is enabled.   

• After that, run Send/Receive All Folders to trigger an immediate sync, because this helps Outlook pull in any messages that were waiting while the app was offline.   

• Reference: Change send/receive group settings - Microsoft Support  

Option 2: If you don't have an admin right, please contact your IT's administrator to follow these steps below:  

1/ Run message trace (admin only)   

• Please involve your tenant admin to run a message trace in the Exchange Admin Center (EAC). This will help determine whether the email was ever received by EOP and provide visibility into its delivery status. Run a message trace and view the results in the Exchange admin center in Exchange Online | Microsoft Learn      
• If the trace shows no record of the email, it confirms that the message did not reach Exchange and may have been blocked or failed at the connector level.     

2/ Review mail flow rules and anti-spam settings     

Sometimes, mail flow rules or spam filters may prevent emails from reaching the inbox.    

• Go to the Exchange Admin Center.    
• Navigate to Mail Flow > Rules and check for any rules that might redirect or block incoming emails.    
• Also review Anti-Spam Policies under Microsoft 365 Defender > Policies & Rules.    
• Make sure there are no filters or rules targeting the affected user’s mailbox.   

3/ Check accepted domains   

• In EAC, go to Mail flow > Accepted domains.    
• Ensure that the user's email domain is correctly listed as an "Authoritative" accepted domain. If it's not, or if there's a misconfiguration, it could prevent incoming mail.    

4/ Check individual mailbox settings  

• Junk Email Settings (Outlook/OWA): While less likely to completely block all incoming mail, an aggressive junk mail setting or a large "Blocked Senders" list could be preventing legitimate emails. Have the user check their own blocked senders list in Outlook/OWA.    
• Mailbox Quota: Is the user's mailbox full? If so, they won't be able to receive new emails. Check their mailbox quota and usage in EAC under Recipients > Mailboxes.    

5/ Check for Account Restrictions    

After an account compromise, Microsoft may automatically restrict email capabilities to protect the environment.  

• Visit the Restricted Users page: Security & Compliance    
• If the user appears on this list, follow the prompts to remove the restriction.    

This action ensures the account is no longer blocked from receiving messages.    

If the issue persists after these checks, ask your IT administrator to submit a support request directly to Microsoft Support team. In this cases, further investigation may be required at the service level, which is not accessible through standard administrative tools. 

The Microsoft Support team has the capability to review backend service behavior, analyze logs not available to administrators, and identify any underlying issues affecting message delivery.     

• A support ticket can be created via the following link: Get support - Microsoft 365 admin | Microsoft Learn 
• In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support    

Or you can contact them via phone number to Microsoft Support: Customer service phone numbers - Microsoft Support - Select your country/region own phone number for support.   

As community moderators, we appreciate your understanding that our access to internal development details is limited. Our primary role is to guide users toward the appropriate resources and support channels. While we may not have visibility into deeper backend analysis, we’ll continue doing our best to support you within the scope of our responsibilities.           

I hope this information is helpful. Please follow these steps and let me know if it works for you. If you have any updates regarding the issue, please feel free to share them with me.            

Thank you for your patience and your understanding. I look forward to continuing the conversation.  

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