Adjust Options in Mailboxes to reduce Spam

​One of our primary ways to stop spammers is to test to see if their mail server is configured to match the mails they are sending.  A lot of spammers, especially those who are not following the CAN-SPAM laws in the U.S., are misdirecting their mail server settings to hide who they really are.  We can detect this and put corresponding messages in the Spam folder; we call this Sender Verification.

​Recently, we have noticed that more of the spammers are correcting these settings in their mail server to make their spam appear more valid.  What I have done is raised the Sender Verification Threshold on my mailbox to be more stringent with the settings it allows to be correct.  Here is how to do the same on your mailbox(es):

1. Right-click on the mailbox you want to change, selecting Options ....
2. Slide the Sender Verification Threshold slider to the left.  A good setting is to slide it to somewhere between the 51%-74% ranges.
3. Press the Save button.

There are far less spammers that have this level of "correct" setting in their mail server, so I have had very good success with this so far.  However, after any change like this, you will have to be extra diligent in watching the Spam folder for the first few days after the settings change, since some legitimate senders will not have their mail server configured correctly -- specifically, we have noticed that several manufacturers and even a couple of IT companies that work with our current users do not have their settings correct; which makes it necessary to add their domains to the Allowed Senders list.
Allowed Senders
Users can add either Domains or individual e-mail Addresses to the Allowed Senders (or Blocked Senders) lists.  To block allow an individual e-mail address: select the message with the address you want to allow in the From field, right-click on the message, select Spam Mail à Allow messages from this Address.  Users can edit the Allowed and Blocked Senders lists by using the Go To à E-Mail à Edit Senders List dialog.  The Allowed and Blocked Senders list are shared company wide so that users can benefit from other user's efforts to block bad e-mail and allow good e-mail.

TIP: View Sender Verification
You can check the Sender Verification value of current messages in your mailbox by turning on the column in the mail listing window.  To do this: 1) Open the View à Settings à Configure ... dialog; 2) Check the Sender % column.  Now that the Sender Verification score is showing in the e-mail table, you can sort by that column to see which messages fall below the new threshold that you are intending to set -- if you see any address and/or domains that should be allowed but are below the threshold, you will want to add the to the Allowed Senders by right-clicking on them and choosing the appropriate option.


​Spam ProbabilityIn addition to Sender Verification, there is the Spam Probability Threshold.  Using the same technique noted above, users can review the Spam % that is being applied to good and bad e-mails.  Analyzing these values will allow users to adjust up or down their Spam Probability Threshold to better manage the sorting of Spam and non-Spam (good) e-mails.
The Spam Probability is set by the Spam Filtering Engine, a sophisticated Bayesian reasoning engine.  This process takes into account the content of an e-mail message and rates its various characteristics to determine if it Spam or not.  Some of the characteristics it looks for include:

• the underlying encoding used in the message,
• the number of misspelled words,
• the presence of hidden text,
• the number of recipients,
• the number of hyperlinks,
• the number of image links,
• and many other characteristics that may contribute to the possibility that a given message is Spam.

The Spam Filtering Engine tunes itself based on the messages that it finds in the Spam and other folders; items in Spam contribute to rate those characteristics found in those messages negatively, messages marked as read in any other folder (including Deleted Items) contribute their characteristics positively.  Each mailbox has its own positive and negative ratings so that the Engine will learn the individual preferences of those users accessing a particular mailbox.  This characterizing process makes it very important that users correctly move Spam e-mails to the Spam folder, or Mark as Spam and Delete the messages, so as not to confuse the Engine.  Think of the Spam Filtering Engine as your assistant in sorting your mailbox... the better you train him, the more effective he will be.