Local-based filters

You can make block/allowlists from emails or IP subnets to forbid or allow them to send or receive emails. With the spamhelodns (HELO DNS Lookup) and spamraddrdns (Return Email DNS Check) options, the FortiGate performs a standard DNS check on the machine name used in the HELO SMTP message, and/or the return to field to determine if these names belong to a registered domain. The FortiGate does not check the FortiGuard service during these operations.

You can also define a list of banned words. Emails that contain any of these banned words are considered spam.

Banned words can only be configured in the CLI.

By default, HELO/DNS and Return-to/DNS checls are done before the block/allow list check. In some situations, such as when configuring a block/allow list to clear an email from performing further filtering, use the following command to give precedence to the block/allow list: config emailfilter profile edit <filter> config smtp set local-override enable next end end

To configure a local-based email filter in the GUI:

1. Configure the email filter profile:

   1. Go to Security Profiles > Email Filter and click Create New, or edit an existing profile.

   2. Enter a name for the profile and enable Enable spam detection and filtering.

   3. In the Local Spam Filtering section, enable the desired filters (HELO DNS Lookup, Return Email DNS Check, Black White List).

   4. If Black White List is enabled, click Create New. The Create Anti-Spam Block/Allow List Entry pane opens.

   5. Select a Type, enter a Pattern, and select and Action.

      

   6. Click OK to save the block/allow list.

      

   7. Click OK save the email filter profile.

2. Configure the firewall policy:

   1. Go to Policy & Objects > Firewall Policy and click Create New.

   2. Set the inspection-mode to Proxy-based.

   3. Enable the Email Filter option and select the previously created profile.

      

   4. Set SSL Inspection to a profile that has deep SSL inspection enabled.

      Deep inspection is required if you intend to filter SMTP, POP3, IMAP, or any SSL/TLS encapsulated protocol.

   5. Configure the remaining settings as needed.

   6. Click OK.

To configure a local-based email filter in the CLI:

1. Configure a block/allow list:

   config emailfilter bwl
       edit 1
           set name "myBAL"
           config entries
               edit 1
                   set status enable
                   set type ip
                   set action spam
                   set addr-type ipv4
                   set ip4-subnet 10.1.100.0 255.255.255.0
               next
           end
       next
   end

2. Configure an email filter profile:

   config emailfilter profile                                             
       edit "myLocalEmailFilter"
           set spam-filtering enable
           set options spambwl spamhelodns spamraddrdns   		
           config smtp
               set action tag
           end
           set spam-bwl-table 1                                           
       next
   end

3. Use the profile in a firewall policy:

   config firewall policy
       edit 1
           .....
           set inspection-mode proxy                                     	
           set emailfilter-profile "myLocalEmailFilter"                 	
       next
   end

To configure banned words:

1. Configure a bannedwords list:

   config emailfilter bword
       edit 1
           set name "banned"
           config entries
               edit 1
                   set pattern "undesired_word"
               next
           end
       next
   end
   

2. Configure an email filter profile:

   config emailfilter profile
       edit "myBannedWordsProfile"
           config file-filter
               set status disable
           end
           set spam-filtering enable
           set options bannedword
           set spam-bword-table 1
       next
   end

3. Use the profile in a firewall policy:

   config firewall policy
       edit 1
           .....
           set inspection-mode proxy                                     	
           set emailfilter-profile "myBannedWordsProfile"                 	
       next
   end