Persons sending junk email will not have the time to analyze bounces, and will simply discard them and not get through to your mailbox. User-Settable Nojunk Level Individual users may set their Nojunk level to between 0 and 10. At level 0 no filtering is done and all email, including all junk email, is permitted to get through unhindered. At level 1 only the most active junk email senders are filtered out. At level 10 junk mail filtering is very aggressive and will detect and filter out most junk email.
Intermediate levels provide intermediate degrees of protection against junk email.
The more advanced features of Nojunk filtering are currently accessible only from the UNIX shell, but a simple web interface is available to customers to perform basic Nojunk configuration. You may use 'njdemo' as the username and password to explore the Nojunk web interface in demo mode. As a result filtering based on message headers is not always sufficient to detect junk email. At levels 8 and higher our Nojunk system also scans message bodies looking for suspicious strings that are often found in junk email. At level 10 this scan of message bodies is very effective and will detect most junk email.