First, Simply use any email client to test your email configuration, like MS outlook. Second, check if email server is specified for your domain by running the following DOS/Linux command.You should see the email server of the domain.
c:\> nslookup -type=mx yourdomain.com
Or, you can manually telnet to your mail server at port 25, 26 and 465 and see if the server is accepting mails for your domain. If the email server is not configured correctly, you usually will get an error message after the rcpt to command.
c:\> telnet youremailserver 25
> helo yourdomain.com
> mail from:
> rcpt to:
> Subject: //enter a test subject
> .....//enter the mail message
> . //enter a dot to indicate the end of mail message