TEST SMTP AUTH CONNECTIVITY

Here's a useful way to test smtp settings when troubleshooting an email client or "scan to email" settings on a multifunction copier/scanner:

Use terminal to telnet to your sendmail server, specify the port you will use to connect.  Many mail servers accept smtp auth requests on port 465 or 587. 

Once connected you can authenticate as a known user by issuing the "auth login" command - the key here is that you need to convert your plain text user credentials using base 64 encoding.  A simple conversion tool can be found at http://www.base64converter.com