é fácil:
swaks --to email1,email3 --from email2 --server smtp --auth LOGIN --auth-user "" --auth-password "" --header "Subject: test" --data "Subject: test
To: email1
Bcc: email3
From: email2
MIME-VERSION: 1.0
Content-Type: multipart/mixed; boundary=\"123456789\"
--123456789
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 8bit
<html>
</html>