Do you get 10 spams per day? Or do you get hundreds of spams per day?
What Is Spam? Spam is email that you don't want. If you get an email from a business and you did not sign up for their list then this is spam. If you get an email from someone you don't know and they are soliciting you to buy something then this is also spam.
What Is the Problem With Spam? The problem is that spam will take up your time and will possibly hide a legitimate email. When your inbox has hundreds of undesirable messages in it, then it can be hard to find a legitimate email.
The best solution is to not get junk email. Filtering undesirable emails can happen in your inbox or before they get to your inbox. The best way to filter out undesired emails is to have a filter setup before the spam reaches your inbox.
The way this works is that a server will filter the email before it is sent on to your inbox. This requires a special junk email filter to be setup. A spam filters such as this needs to be very intelligent in order to make practically zero mistakes.
If your spam folder is not intelligent then you could unknowingly have a legitimate email put into your spam folder. If your spam filter makes the mistake of putting good and desired messages that you want into the junk folder then you should consider getting a better spam filter.
An intelligent spam folder will use a point system to determine whether or not a spam is a likely message that needs to be put into the junk folder.
Some of the filtering steps are very logical, such as, is the IP address of the sender from a known spammer? Or does the message use words that are commonly associated with spam type messages. If there's an image in the email, an intelligence email filter will utilize OCR to scan the picture for text and then check to see if the words in the image are commonly associated with spam messages.
I have seen a really good email filter catch a legitimate email and mark it as possibly spam, but then it also continued to send that email to the inbox with an attachment that explained why it looked like spam and that it would like to know if this email was spam or not so it could improve its filtering on future emails.
Jacob Barr, iRapture.com