Client is receiving multiple e-mails from one exact spammail

[Berto2715]

Hi, 

Our customer uses office 365 and recently received a spam email, only now that email continues to flow in with the exact times it's send from. For the past few days they have been getting about 10/20 emails from the same sender and content every second and it adds up to thousands of emails. SMTP, Captcha and an antivirus is set up. Until now the mails keep pouring in, has anyone had the same kind of problems or is there a solution?

Kind regards!

[#2]

@Berto2715 you need to configure an anti-spam policy for your inbound to block such spam emails coming from a specific sender. Please refer to the below link

https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-your-spam-filt...

[#3]

Hello, @Berto2715, there are several ways to solve your problem. You should configure outbound spam filtering, filtering based on verified IP addresses, spoof intelligence, spam filter policy and rules, modify the default connection filter policy in Microsoft 365 Defender and manage all the errors in spam filtering.

It is not an easy process, so I recommend reading this useful article to learn more details on all the possible workarounds.

Normally, Office 365 uses basic Exchange Online Protection to prevent organization from spam, it includes the following settings: Connection Filtering, Anti-Malware, Mail flow rules and Content Filtering.

Besides, ATP which has more powerful spam protection is also an option.