Exchange Online Protection (EOP) and Microsoft 365 protect you from malicious material by issuing warning notifications within your mailbox messages. This safety tip color-coded, and will warn you about potentially harmful messages.
Suspicious mail (red safety tip)
This is a warning that the message you received contains suspicious material, such as a phishing scam. Delete this kind of email message from your mailbox without opening it.
Spam (yellow safety tip)
This message indicates that the message was marked as spam. If you do not recognize and trust the sender of the message, do not download any files or pictures in the message, and do not click any links in the message.
Safe Mail (green safety tip)
This is a notification that the message is valid and from a trusted sender.
Unfiltered mail (gray safety tip)
This means that the system did not check the message because it is on a users Safe Senders list, or a rule exists to bypass filtering.