Hello @Roger Roger,
You can check the Audit logs from Azure Active Directory.
Go to https://aad.portal.azure.com, go to Users > Audit Logs.
To get the current status of the user through PowerShell:
1. Connect to Office 365 through PowerShell. Ref article - https://docs.microsoft.com/en-us/office365/enterprise/powershell/connect-to-office-365-powershell
2. After connecting to Office 365 services, enter command "Get-MSOLUser -UserPrincipalName xxxx@contoso.com | select BlockCredential"
3. If this is True, means user is blocked.
I would also recommend you to check if the user account was compromised, because bulk emails are considered as Spam and that's the reason the account is getting blocked.
Check if there forwarding rule created in Outlook on the Web. Also, you can enabled MFA to ensure that the account doesn't get compromised.
Thanks!
