Spam Filtering

Your incoming Unix email is checked for spam. Mail messages that are identified as possible spam are diverted to a file (Caughtspam) in your mail directory. Since spam filtering is not an exact science, there's always the possibility of false negatives or false positives; in other words, spam may be misidentified as legitimate email or vice versa. False negatives are easy to deal with; simply delete the offending message. To deal with false positives, you should check the Subject field of each suspicious message; if they all turn out to be spam, you can safely delete the file containing same.

If you use alpine or SquirrelMail to read your email, the Caughtspam file appears as a mail folder in which you can view the subject lines in the usual way.

If you don't use alpine or SquirrelMail, here's how you can check for false positives:

  1. Run the command mvspam from a shell window. This safely moves the suspected spam file to a holding directory (~/.holdspam/).
  2. Run the checkspam command. If you have an inordinately large amount of spam, you should pipe the results through the more command, i.e., use the checkspam | more command sequence.
  3. If there are no false positives, run the rmspam command, which will safely delete the suspected spam. It will ask you whether you're sure you really want to delete your spam file; in other words, it gives you a chance to change your mind.

If there are false positives, there are a few things you can do to read the associated email message:

  1. If you are comfortable reading email in emacs, you can run RMAIL or vm on the file:
    • If you want to use RMAIL, issue the command C-u M-x rmail from within emacs.
    • If you want to use vm, issue the command M-x vm from within emacs, followed by the keystroke v.
    • In either case, when prompted for a file name, enter ~/.holdspam/Caughtspam as your response.
  2. If you would rather not read mail from within emacs, you can use the more command to look at the ~/.holdspam/Caughtspam file. You can also examine the file with a text editor that you like. In either case, you would simply scroll down (or do a search) until you find the subject header of interest.
  3. If the spam-filtering software consistently identifies one or more addresses incorrectly as spam sources, you can create a file ~/.whitelist containing those addresses; the spam-filtering software will then assume that any mail coming from said addresses is legitimate.

Of course, once you have done this, you should use rmspam to get rid of the spam.