The "email-send-method" setting:

Determine the method used to send email.  Allowed values are
"off", "relay", "pipe", "dir", "db", and "stdout".  The "off" value
means no email is ever sent.  The "relay" value means emails are sent
to an Mail Sending Agent using SMTP located at email-send-relayhost.
The "pipe" value means email messages are piped into a command 
determined by the email-send-command setting. The "dir" value means
emails are written to individual files in a directory determined
by the email-send-dir setting.  The "db" value means that emails
are added to an SQLite database named by the* email-send-db setting.
The "stdout" value writes email text to standard output, for debugging.