sendmail − an electronic mail transport agent   sendmail [flags]
[address ...]   Sendmail sends a message to one or more
recipients, routing the message over whatever networks are
necessary. Sendmail does internetwork forwarding as necessary to
deliver the message to the correct place.  Sendmail is not
intended as a user interface routine; other programs provide
user-friendly front ends; sendmail is used only to deliver pre-
formatted messages.  With no flags, sendmail reads its standard
input up to an end-of-file or a line consisting only of a single
dot and sends a copy of the message found there to all of the
addresses listed. It determines the network(s) to use based on
the syntax and contents of the addresses.  Local addresses are
looked up in a file and aliased appropriately. Aliasing can be
prevented by preceding the address with a backslash. Beginning
with 8.10, the sender is included in any alias expansions, e.g.,
if ‘john’ sends to ‘group’, and ‘group’ includes ‘john’ in the
expansion, then the lette