Why do I get spam messages from my own address?

The following article explains why you will receive spam messages that appear to be send from your own email address and how to prevent them. This type of spam is referred to as spoofing, and is one of the more common types of spam you might see. It takes advantage of the fact that many users will trust their own address or domain name.

Why aren't they marked as spam?

In most cases, the server is identifying the messages as spam, but some other spam filter setting is preventing the spam filter from dealing with the message. The most common place to fine this is trusted senders. If you have your own email address, or domain name in the trusted senders, the server spam filters can't do their job. You would want to remove this:

You might also find it in the domain trusted senders:

After this, you would want to review any Content Filters you have set up, as they could be skipping spam checks.