Recently many merchants have complained of receiving spam from their own email address. For instance if my email address is firstname.lastname@example.org then the email is also coming from email@example.com
Spammers can send email with the from address as anything that they would like and this is a easy way for them to get the emails delivered.
Why do the emails get delivered to my inbox even though they are spam?
In most cases people setup their own address as a trusted sender. A trusted sender is one in which no spam checks will be executed and the email is always delivered to the inbox. Spammers know this and they use your own address as the from address so that the spam will be delivered.
How do I fix this?
Remove your own email address and/or domain name from the trusted senders box inside of webmail. Once this is done email from this address will be checked for spam and you should see an immediate decrease in the amount of spam.