Traditionally, Unix mail
and derivatives (and many other Unix tools) use the /usr/bin/sendmail
interface, provided by almost all mail transfer agents (MTAs – postfix, exim, courier, and of course sendmail).
That is, the mail
program doesn't speak any network protocol – it feeds the message to sendmail
via stdin, and lets it handle actual delivery. (This goes back to the days when some mail used SMTP, some used UUCP, some used BITNET...)
Once a message is queued through sendmail
, the MTA handles actual message transmission, whether through SMTP or something else. Depending on configuration, it may either connect directly to the destination MTA, or relay mail through another host (also called a smarthost).
Direct connection is more common on servers; relay via smarthost is more common on personal computers on home connections – relaying through your Gmail or ISP/work email account is essential to avoid the blanket "dynamic IP" anti-spam filters.
(Some MTAs such as esmtp
or nullmailer
are built specifically for home users and always use a relayhost. These don't support receiving mail and are a lot lighter on resources.)
mailx → [/usr/bin/sendmail] → local MTA queue → [SMTP] → recipient MTA → recipient inbox
mailx → [/usr/bin/sendmail] → local MTA queue → [SMTP] → Gmail or ISP/work servers → [SMTP] → recipient MTA → recipient inbox
Other programs, mostly the user-friendly graphical clients such as Thunderbird or Outlook, always connect directly to a relay/smarthost SMTP server (again, usually Gmail or ISP/work SMTP server), which transmits the message on your behalf.
Native SMTP support is present in heirloom-mailx
, but not in the traditional bsd-mailx
.
app → [SMTP] → Gmail or ISP/work servers → [SMTP] → recipient MTA → recipient inbox
The third method – connecting directly to recipient's server – is almost never used, and no MUA supports it. On personal computers, using it would cause your message to get rejected (a lot of spam is sent from infected home user IP addresses).
app → [SMTP] → recipient MTA → caught by the spam filter
If you are attempting to modify your HOME, you can do
export HOME=/home/...
either in your shell, or in your ~/.profile file and/or ~/.bashrc (or appropriate login shell).
(The above code will work for bash and similar shells, which are default in Debian; you would otherwise do `setenv HOME $HOME:/extra/path I think on csh-like shells in other distros.)
edit -- However this is probably not the way to do it. See other answers. Do not use this answer.
Best Answer
I just tested this in Ubuntu 14.04 and using the -S parameter worked for me:
So, the following command sets the from address to "test@exmaple.org":