I know that is possible to send mails using the oracle-db by UTL_SMTP, and there are several examples of such usage everywhere.
My question is: Can I call the GNU/Unix/Linux Sendmail to perform a similar action?
Why do you want to use sendmail? Is it just because it is simpler than UTL_SMTP? You should really look into UTL_MAIL.
To send mail from an Oracle db, you might: