That's why I have configured Pegasus Mail to ask me each time I send a message whether I want to keep a copy of it.
Keep a Copy of a Sent Message in Pegasus Mail
To make Pegasus Mail ask you, too:
- Select Tools | Options from the menu in Pegasus Mail.
- Go to the Outgoing mail | Copies to self ('outbox') category.
- Make sure Ask at send time whether or not to make a copy to self is selected.
- Click OK.

