"Modify" actions change the message or its attachments. The original sender will still receive the modified message, assuming that the message does not trigger other rules with "Intercept" actions.
Note that the "Modify" actions may destroy the existing DKIM signatures in email messages. If this occurs, the messages cannot pass DKIM verification by the downstream mail server.
Clean cleanable Viruses, delete those that cannot be cleaned Action
Delete matching attachments Action
Sanitize attachments Action
Insert X-Header Action
Insert stamp in body Action
See Inserting a Stamp.
Tag subject Action
Terminal "Modify" actions have higher execution priority over non-terminal actions. When a terminal "Modify" action is triggered, there is no need to perform any other actions. However, non-terminal actions can be combined, such as Delete matching attachments and Insert stamp in body.