Limit international spam with Block Top Spamming Countries and Only Allow Emails in Specific Languages settings.
Block Top Spamming Countries
The Office Protect team pre-determined a list that includes countries with the highest ratio of spam emails versus real emails. You can tweak the list to fit your organization's reality. We will adjust the Exchange Anti-Spam policy accordingly.
All emails from the countries listed will be blocked if the setting is enabled. The recipient will not receive any notification that an email was blocked.
You can find the setting in the Security Center, in the Threat Management/Policy/Anti-Spam section.
Operation to look for in the Unified Audit Logs: Set-HostedContentFilterPolicy
Microsoft’s documentation about Anti-Spam policy: https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-your-spam-filter-policies?view=o365-worldwide
Only Allow Emails in Specific Languages
Reduce spam and illegitimate emails by limiting the email languages you accept.
Office Protect, by default, will only allow English to be sent, but you can allow more languages as needed. We will update the Anti-Spam policy accordingly. Also, note that all emails identified with a language not present in the list below will be blocked automatically. The recipient will not receive any warning nor notification that one of their inbound email was blocked.
You can find the setting in the Security Center, in the Threat Management/Policy/Anti-Spam section.
Operation to look for in the Unified Audit Logs: Set-HostedContentFilterPolicy
Microsoft’s documentation about Anti-Spam policy: https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-your-spam-filter-policies?view=o365-worldwide