You can specify any extra header you may need with
$echo "This is the main body of the mail" | mail -s "Some random subject" -a "From: email@example.com" firstname.lastname@example.org
In my version of mail, the following options work for controlling the source / reply addresses
-a switch, for additional headers to apply, supplying a From: header on the command line that will be appended to the outgoing mail header
$REPLYTO environment variable specifies a Reply-To: header
so the following sequence
mail -aFrom:email@example.com -s 'Testing'
The result, in my mail clients, is a mail from
firstname.lastname@example.org, which any replies to will default to
NOTE by @Rui F Ribeiro: only the root user is able to change the From field.