options for handling spam
Ways to prevent those unwanted emails from showing up.
DoIT has some info on how to improve their spam filter at http://kb.wisc.edu/page.php?id=2383
Though the gist of it for reporting spam is forward the original message to firstname.lastname@example.org
If the messages are business solicitations, from "real" companies, filters based on return email address can be very effective since they'll use a consistent return address. It takes a couple clicks to setup in Thunderbird per company, but then you'll no longer see ones from that company.
1. Click on one of the business emails that you'd like to no longer see (ie highlight it) while still staying in the mailbox view of messages
2. Go to the "Message" menu and select the bottom option, "Create Filter From Message..."
3. It'll automatically grab the from address, all that needs to be edited is the "Perform these actions" section. Set the first drop down to "Move Message To", and in the select your "JunkMail" folder from the list of mailboxes. Leave "Apply Filter" set to "Checking Mail or Manually Run"
4. Click OK
5. Click the "Run Now" and then close the filter dialog.
This will make it so that when you check mail, you may see the unwanted messages from the same handful of companies flash by, and Thunderbird will have automatically put them in the JunkMail folder where they belong.