Why am I getting SPAM from my own email address?

This is called "spoofing".  When email is sent, it is quite easy for the sender to put false data in the "From" field.  It's really no different than putting a fake return address on an envelope sent through the US Postal Service. 

Many of the spamming programs are designed to run with a "dictionary" style approach:
 
Send to: aaaaaa@yourdomain.com , then
Send to: aaaaab@yourdomain.com , then
Send to: aaaaac@yourdomain.com ...
Send to: aabbbc@yourdomain.com ...etc....

When this is combined with use of the same address as the sender as the recipient, the result appears to be folks are sending themselves the spam when a valid email address is hit.

Other approaches randomize the sender with one set of forged addresses while the recipient is another.  In that case, if you are unlucky enough to have your email address forged for the sender, you may receive bounce messages for emails you did not send.

Most of these forgeries are very easy to recognize from the full mail headers which are normally not displayed by email applications. 

To fight this sort of forgery and spam, our mail platform is able to use some newer techniques which help identify the legitimate emails from the forgeries.  One of these techniques is called SPF (Sender Policy Framework).  Using an additional record in your domain's DNS information, mail servers can verify which sources are legitimate and which are not allowed.  This is one of many ways which Digital West is fighting to keep junk mail  out of your inbox. 

Read more about SPF at http://support.digitalwest.net/KB/a164/what-is-spf.aspx

If Digital West is hosting your DNS and you always will be sending mail through specific servers, contact support to have strict SPF for your domain.