Mail flow rules (also known as transport rules) help us identify and on messages that flow through your Exchange Online organization. Mail flow rules are the Inbox rules that are available in Outlook and Outlook on the web. The main difference is mail flow rules on messages while they're in transit, and not after the message is delivered to the mailbox. Mail flow rules contain a richer set of conditions, exceptions, and actions, which provides you with the flexibility to implement many types of messaging policies.
You can create a mail flow rule (also known as a transport rule) that sets the spam confidence level (SCL) of an email message. The SCL is a measure of how likely a message is to be spam. Spam is unsolicited (and typically unwanted) email messages. The service takes different actions on a message depending on its SCL rating. For example, you might want to bypass spam content filtering for messages that are sent from people inside your organization because you trust that a message sent internally from a colleague isn't spamming. Using mail flow rules to set the SCL value of a message gives you increased control in handling spam.
How Use Mail Flow Rules To Set SCL In Messages
Go to your Office Portal and select Admin app (this will only be visible if you are an admin in your organization).
Once you reach your Admin , click on Show more.
Click on Admin .
Click on Exchange.
In the screen that appears, go to Mail flow category, click on Rules.
In the rules, click on ‘+’ and then select Create a new rule.
Specify a name for the rule.
Choose More options, and then under Apply this rule if, specify a condition that will trigger the action you'll be set for this rule (which is to set the SCL value).
Do the following, select Modify the message properties > set the spam confidence level (SCL).
In the specify SCL dialog box, select one of the following values, and choose ok:
Bypass spam filtering - This sets the SCL to -1, which means that content filtering won't be performed.
0-4 - When you set the SCL to one of these values, the message will be passed along to the content filter for additional processing.
5, 6 - When you set the SCL to one of these values, the action specified for Spam in the applicable content filter policies will be applied. By default, the action is to send the message to the recipient's Junk Email folder.
7-9 - When you set the SCL to one of these values, the action specified for High confidence spam in the applicable content filter policies will be applied. By default, the action is to send the message to the recipient's Junk Email folder.
Specify additional properties for the choose Save.