Urgent Assistance Required – Exchange Online Account Blocked from Sending Emails (550 5.1.8 AS(42004))

Question

Urgent Assistance Required – Exchange Online Account Blocked from Sending Emails (550 5.1.8 AS(42004))

ABDUL SAMAD - 0

Hello Microsoft Support Team,

I am a university student using a Microsoft 365 Outlook account provided by King Fahd University of Petroleum and Minerals (KFUPM).

Recently, my email account was compromised after an unauthorized individual obtained my credentials and used SMTP authentication to send approximately 2,000–2,500 spam emails.

As a result, Microsoft Exchange Online appears to have automatically blocked outgoing emails from my account.

I have already taken the necessary security measures, including changing my password, enabling multi-factor authentication through Microsoft Authenticator, and reviewing my account security settings.

However, I am still unable to send emails. Every outgoing message fails with the following error:

550 5.1.8 Access denied, bad outbound sender AS(42004)

I understand that this error may indicate that my mailbox has been added to the Microsoft Defender Restricted Entities list.

Unfortunately, I have already contacted my university's IT support department, but the issue remains unresolved.

I would therefore like to ask:

Is there any way for Microsoft Support to review and remove this restriction directly?

Can I submit an individual support request for my university-managed Microsoft 365 account?

If administrator authorization is mandatory, is there an official Microsoft escalation process I can request when my university's IT department is unable to resolve the issue?

This restriction is significantly affecting my academic and research-related communication.

I would greatly appreciate any assistance or guidance on restoring my outgoing email functionality.

Thank you.

Moved from: Outlook | Web | Outlook.com | Email

0 comments

1 answer

Your answer

Answer 1

Hello ABDUL SAMAD
Thank you for posting question to Microsoft Q&A Forum.

Since this is a university-managed Microsoft 365 account, the restriction cannot normally be removed by you directly. Please contact your university's Microsoft 365/Exchange administrator and ask them to check your account under Microsoft Defender > Restricted entities and unblock it after confirming that the account has been secured.

If your university administrator is unable to remove the restriction, they should open a support request with Microsoft from the Microsoft 365 admin side for further check. Microsoft Support would not normally bypass the tenant administrator and remove a restriction from a university-managed account based solely on an individual user's request.
Please make sure that the person from IT department you are contacting has the access to Microsoft Defender portal.

Let me know if you have any further questions.

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.