Anti-spam and anti-malware protection

Microsoft Exchange Online provides built-in malware and spam filtering capabilities that help protect inbound and outbound messages from malicious software and help protect your network from spam transferred through email. Administrators do not need to set up or maintain the filtering technologies, which are enabled by default. However, administrators can make company-specific filtering customizations in the Exchange admin center (EAC).

Anti-malware protection

Using multiple anti-malware engines, Exchange Online offers multilayered protection that's designed to catch all known malware. All messages transported through the service are scanned for malware (viruses and spyware). If malware is detected, the message is deleted. Notifications may also be sent to senders or administrators when an infected message is deleted and not delivered. You can also choose to replace infected attachments with either default or custom messages that notify the recipients of the malware detection.

For more information about anti-malware protection, see Anti-Malware Protection.

Anti-spam protection

Exchange Online uses proprietary anti-spam technology to help achieve high accuracy rates. The service provides strong connection filtering and content filtering on all inbound messages. Outbound spam filtering is also always enabled if you use the service for sending outbound email, thereby helping to protect organizations using the service and their intended recipients.

For more information about anti-spam protection, see Anti-Spam Protection.


Messages identified as spam and messages that match a transport rule can be sent to the administrator quarantine. Administrators can search for and view details about quarantined email messages in the EAC. After locating the email message, you can release it to specific users and optionally report it as a false positive (not junk) message to the Microsoft Spam Analysis Team if it was misidentified as spam.

There is also a spam quarantine for end users, which lets them manage their own spam-quarantined messages. End user management of spam-quarantined messages can also be performed via end-user spam notification messages (if they are enabled by an administrator).

For more information about the quarantine feature, see Quarantine.

Feature availability

To view feature availability across Office 365 plans, standalone options, and on-premises solutions, see Exchange Online service description.