This is useful if your default address is not the address that is
subscribed to a list. If you use the sendmail binary, you must have
suitable privileges for the -f parameter.
+ Default is the value of the 'sendemail.envelopesender' configuration
+ variable; if that is unspecified, choosing the envelope sender is left
+ to your MTA.
--to::
Specify the primary recipient of the emails generated.