Quick questions
You have received message about the undelivered email that appear to originate from your email address. In addition the name of your computer or provider mentioned in such message is wrong. Don’t pay any attention on such letter, it wasn’t sent from your email address – it was sent by spammers.
Unfortunately it’s possible to forge the sender address. If the receiving server does not make additional checks (SPF, DKIM) it’s possible to send letter from any email address.
The mail server having rejected the letter can send to the sender the bounce message of non-delivery (Non-Delivery Report, NDR). Since the address of the sender is forged, the user can receive set of messages on non-delivery. Such incorrect automated sending of bounce messages by mail servers is called backscatter.
See here for more details about spam.
Some advices of how to reduce spam amount in the mailbox.