How can I receive an email alert whenever a new posting matches my requirement?

After you search classifieds with selected fields, you have to save this search as email alert; you can do this by selecting "Save this search as email alert" which is available just below the search fields. (You can see this box only in the search result page).

Enter your email id in the box and click on "Create alert"

A verification mail will be sent to your mailbox with a link, click on the link to confirm and activate your email alert.

That's it. You will receive an email notification as soon as a new matching classified is posted.

Note: You will not receive email alert until you click on the verification link.