Information Technology Services

ITS System Information

How can I create a filter to get rid of unwanted mail?

The filter program allows you to define a set of rules by which all incoming mail is screened, and a subsequent set of actions to perform based on whether the conditions are met or not. Filter also has the ability to mail a summary of what actions it performed on the incoming mail as often as you'd like.

1. To setup a mail filter, you need to first connect to the server (either mail.rochester.edu or troi.cc.rochester.edu using SSH (secure shell) or Telnet. For instructions, please see Connecting using SSH.

2. Once you have connected to the server, you will need to create a .forward file (a file named .forward) using the "Joe" text editor. You can do so by typing the following command at the mail% or troi% prompt:

   joe .forward

3. In the .forward file, put the following line (with the quotations and all on one line):

   "|/usr/ucc/bin/filter -vo /var/tmp/filter.userid"

   Replace "userid" with your login name. This file tells the system that all mail received is to go to through the filter program before it goes to your inbox.

4. Then, save this file. In Joe this is done by typing Control-K (type the letter K while holding down the control key) then typing the letter X.

5. Next, you need to create a filter-rules file (a file named filter-rules) in the .elm subdirectory of your home directory. You must first create the .elm directory by typing:

   mkdir .elm

6. Now you can edit the filter-rules file by typing:

   joe .elm/filter-rules

7. In this file you can put commands in the following form:

   if (to = "mail@entrepreneur.com") then delete
   if (subject contains "key-word") then save
   

   "~/Mail/folder"
   always forward "cymi@mail.rochester.edu"

   • The first rule tells the filter program to delete any mail from mail@entrepreneur.com.
   • The second rule tells the filter program if you see key-word the save that message to a folder.
   • The third message will always be executed. This rule says always forward the message to cymi@mail.rochester.edu.
   • NOTE: If your command takes up more than one line, be sure to indent any lines after the first one so that it will be interpreted as part of the same command.

   You can filter based on the fields from, to, and subject.
   The actions you can take are:

   • save folder-name -- Save into the folder "folder-name"
   • delete -- Delete the message completely
   • savecopy folder-name -- Leave a copy in the inbox and also save a copy to the folder "folder-name"
   • execute command -- Execute a UNIX shell command
   • forward user@address -- Forward message to "user@address"
   • forwardc user@address -- Leave a copy in the inbox and also forward a copy to "user@address"
   • leave -- Leave message in inbox; take no action

   When you are finished editing your filter-rules, save the file by typing Control-K then X.

8. To test your filter, you can type in the command

   filter -r

   and you should get the following output for the above rules:

   Rule 1: if (to = "mail@entrepreneur.com") then
   Delete

   Rule 2: if (subject = "key-word") then
   Save ~/Mail/folder

   Rule 3: ** always **
   Forward cymi@mail.rochester.edu

   If you get an error message, there may be a typo in your filter-rules file. Repeat steps 6 and 7 and doublecheck your rules, or write to problem@mail.rochester.edu or problem@troi.cc.rochester.edu and include the error message.

For more detailed information on the filter command you can type:

man filter