Answer Description
Changing the account password will most likely solve the issue, but better preventatives should be put in place as soon as possible. Spam filters typically ignore local emails, which is why this is not the correct answer.
Wikipedia
Email filtering is the processing of email to organize it according to specified criteria The term can apply to the intervention of human intelligence, but most often refers to the automatic processing of incoming messages with anti-spam techniques - to outgoing emails as well as those being received Email filtering software may reject an item at the initial SMTP connection stage or pass it through unchanged for delivery to the user's mailbox - or alternatively: redirect the message for delivery elsewhere quarantine it for further checking edit or 'tag' it in some way
Email_filtering - Wikipedia, the free encyclopedia