Sendmail sends a message to one or more recipients, routing the message
over whatever networks are necessary. Sendmail does internetwork for-
warding 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-
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 mes-
sage 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 letter will also be delivered to 'john'.