In the trigger settings, you can insert an e-mail in the "Source e-mail" field, but it does not accept a placeholder, even if it's an e-mail type.

1. Access or create a trigger;
2. Click actions if positive;
3. Fill in the "Source email" field with a placeholcer. For example: "{!email}";
4. Run the trigger;
5. The email will not be sent.

The "Source e-mail display name" field accepts placeholders and can be used to cover most scenarios in which you'll need a placeholder in this field.