Short answer: Yes.
Long answer: No. It depends on the MUA
. Intead of invoking an old /bin/mail- type program (for which the short answer applies), mail
can invoke a more intelligent MUA, such as mailx (formerly known as nail), which can contact a remote SMTP server if told do so in its config file. From the nail man page:
smtp Normally, nail invokes sendmail(8) directly
to transfer messages. If the smtp variable
is set, a SMTP connection to the server
specified by the value of this variable is
used instead. If the SMTP server does not
use the standard port, a value of
server:port can be given, with port as a
name or as a number.