Yes. The following procedure will allow your Users to add email addresses to a global Blacklist by sending an email.

1.) Create a new account - e.g. blacklist@yourdomain.com
2.) Create a text file with a short path location - example c:\filter\filter.txt
3.) Create the Global Black list rule - Go to [Mail Service] [filters] [Rules] Add a rule with the following options:

Action - Reject
Item - Sender
Function - Contain string from file
String - c:\filter\filter.txt
   

Create content filter - Go to [Mail Service] [Filters] [Content Filter] Add a filter with the following options:

Where Sender is Local

And

Where Recipient matches blacklist@yourdomain.com

Add %%subject%% to a file

Filename - c:\filter\filter.txt

Text - %%subject%%

Once this is complete any of your Users can add an Email address to this blacklist by sending an email to blacklist@yourdomain.com with the subject set to the address to be blacklisted. The content filter will strip the subject line from the email and append it to the blacklist text file and emails from that address will rejected in future.