To cancel your JobMail, sign in to your account and click your name at the top right of the page. Now click Saved Searches. From here, un-tick Email me new jobs next to the Saved Search you wish to turn off. You can also select Delete to remove both the JobMail email and saved search.
Alternatively, you can unsubscribe by opening your JobMail, scrolling to the end of the email and clicking the Unsubscribe link. If you have multiple Saved Searches, you may be receiving a JobMail for each Saved Search and will need to unsubscribe from each one. For example, if you have 2 saved searches, one for Accounting jobs in Melbourne, and one for Accounting jobs in Sydney, you will receive two JobMails each day. Therefore, you will need to click unsubscribe from both emails.
Related FAQ: How do I unsubscribe from SEEK emails and notifications?