If you don't have access to the mailx (eg: Windows hosts, etc), you could try sending a test email using Telnet (thanks to RFC15 circa 1969).

Without explanation (you can search for other sites with far more info):

The following assumes: 1. You are running a mail relay at 10.0.0.1 (smtp port 25/tcp). 2. Your mail relay will accept email for the sending domain work.example.com). 3. Your mail relay can talk to other mail relays. 4. That telnet is installed (not the default for recent Windows versions).

telnet 10.0.0.1 25
HELO work.example.com
mail from: ikarus@work.example
rcpt to: ikarus@home.example
data
subject: This is a test
This is a test.
Sent by iKaruS@work.
.
quit