Can't send emails after changing password (Outlook business account)

Good day Roger, 

Changing your password doesn't normally prevent you from sending email. Since the issue started after the account was compromised, Microsoft 365 can restrict email sending to help protect the service. In this situation, you can usually continue receiving email, but an administrator needs to review the account and remove the restriction before sending is restored. 

Here are the steps you need to follow: 

Step 1: Check the error message 

Send a test email from Outlook on the web and note any delivery failure message. 

If you see an error code such as 550 5.1.8 or a message indicating that the sender isn't allowed to send email, please share the full error message with your organization's IT administrator.  

Note: 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  

Step 2: Ask your administrator to check Restricted entities 

Please contact your organization's IT administrator and ask them to: 

Sign in to the Microsoft Defender portal. 

Go to Email & collaboration > Review > Restricted entities. 

Search for the affected account. 

If the account appears in the list, review the details, confirm the account has been secured and select Unblock. 

Step 3: Verify the account has been fully secured 

Please ask your IT administrator to: 

Sign out all active sessions for the account. 

Review mailbox rules for anything unexpected. 

Verify that no unauthorized forwarding addresses have been added. 

Review recently sent messages for unusual activity. 

Enable multifactor authentication if it is not already enabled. 

The following articles may be helpful: 

Remove blocked users from the Restricted entities page - Microsoft Defender for Office 365 | Microsoft Learn 

Respond to a compromised email account in Microsoft 365 - Microsoft Defender for Office 365 | Microsoft Learn 

Step 4: Sign in your work account again 

After the administrator confirms the account isn't restricted: 

Sign out of Outlook on the web > Open your browser settings > Select Privacy, search and services > Clear all browsing data > Set the time range to All time.   

Ensure cookies, cache and saved sessions are selected.   

Sign out of all accounts in the browser afterward.   

Close all browser windows and reopen the browser. 

Sign back in to Outlook on the web using the updated password > Send a test email. 

Note: The instructions for clearing the browser cache are based on Microsoft Edge. Other browsers may have similar options. If you cannot locate the setting, please let me know which browser you are using. 

If the issue continues after these steps, please ask your organization's IT administrator to create a support request through Microsoft 365 admin center > Support > Help & Support for further investigation. 

A technical support engineer can perform a remote session to investigate the situation, verify the backend configurations, and run any necessary synchronization tools to resolve the problem. If the issue requires further attention, they can escalate it to a specialized team for deeper analysis.    

If you have any questions, please don’t hesitate to reach out at any time. 

Thank you for your patience and understanding. 

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