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To create a filter:
- Click the gear icon drop down arrow in the top right hand side of the screen
- In the setting screen click Filters
- Click Create a new filter
- Specify a the search box at the top of the page.
- Specify the criteria to define matching message (eg from Jack)Click Next Step e.g. From, To, Subject, Has the Words, etc.)
- Click Create Filter.
- In the next screen specify the action to take for matching messages (eg e.g. Apply label).
- Click the blue Create Filter button.
Whenever you receive a message that matches the criteria, the defined action will take place.