Outlook internet emails not being sent

[Reggie]

My configuration is running SBS 2000 server with 5
workstations running Windows 2000 and Outlook 2002. The
issue is when I compose and email and send it (example:
(e-mail address removed)) the email is not put in the sent folder
but it is never received by the recipient. However, if I
send an email to myself from (e-mail address removed) and reply to
it, the message is put in the sent folder and received by
the recipient. Any idea what may be happening? Is MS
Exchange "swallowing" the emails? By the way, in the ICW
wizard I selected "Use SMTP for Internet Mail". Is this
the issue?

Thanks in advance

Reggie