1. Go to Setup > Automation > Workflow Rules.
2. Click Create Rule.
3. In the Create New Rule page:
Select Email from the Module dropdown list.
Enter the Rule Name and Description.
Click Next.
4. Select Incoming email or Outgoing email and the condition for When do you want to execute the rule?
5. Click Next.
6. In Condition:
Click Yes or No for Would you like to set conditions for email fields?
Specify the email fields if you chose Yes.
Select the module in Apply this rule to.
Select All for Which (module) you want to apply this rule to? or specify the conditions.
Click Next.
7. Select an Instant Action.