You can send an email from the command line with TelNet or NetCat.
Everything is explained here.
hanoo@hp_laptop% nc 127.0.0.1 25
220 hp_laptop.localdomain ESMTP Postfix
EHLO man
250 hp_laptop.localdomain
MAIL FROM: <netcat@postfix.com>
250 2.1.0 Ok
RCPT TO: <target@host.com>
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
This is the body of my mail,
this is the second line...
.
250 2.0.0 Ok: queued as 9C12E7F404