Office 365 Spam filter checks for message characteristics consistent with spam by using spam filtering. You can change what actions to take on messages identified as spam, and choose whether to filter messages written in specific languages, or sent from specific countries or regions. You can also turn on advanced spam filtering options if you want to pursue an aggressive approach to spam filtering. Additionally, you can configure end-user spam notifications to inform users when messages intended for them were sent to the quarantine instead.
I hope this information helps!
Regards,
Lewis