MAPISEND (Back Office/Exchange Resource kit)

Send email from the command line.

syntax
      MAPISEND -u "<profile>" -p <password>
         -r <recipient> -s "<subject>" -m <text message> [options]

      MAPISEND -u "<profile>" -p <password>
         -r <recipient> -s "<subject>" -t <text file> [options]

options
      -i  interactive login (prompts for profile and password)
      -c  cc: list
      -f  File Attachment - path and file name(s)
      -v  generates verbose output

"profile" is the profile name (user mailbox) of sender
"subject" is the subject line 
"recipient" is one or more recipient(s) 
if more than one recipient - separate with ';' 

Example

mapisend -u "john doe" -p MyPassword -r billg@beast.com -s "Test message" -t c:\MyMail.txt

"The new electronic interdependence re-creates the world in the image of a global village" - Marshall McLuhan

Related Commands:

The command
START mailto:billg@beast.com
Will send email but requires the user to complete and send the message.

Mapisend requires MAPI - i.e the MS Exchange/Outlook client needs to be installed.
If you need this for a server and the idea of installing MS Office sends shivers then there are 3rd party command line mailers that use SMPT e.g. BLAT and CommandMail

Equivalent Linux BASH commands:

sendmail