If you are receiving a lot of 'New Quote Request' emails, the most likely cause is that you have created a Saved Search, which will automatically turn on 'Instant Alerts' for jobs that match your saved search.
To check this and change your settings go to Menu>Account Settings>My Communication Preferences. The top section 'Saved Searches' will show a list of your Save Searches as well as checkboxes for 'Instant Alerts' and 'Daily Summary'.
When a new job is listed that matches the paramaters of your Saved Search you will receive an email notifying you soon after. i.e. One new job = one email, so depending on how broad your search is, you may receive quite a few.
Once a day, you will receive an email summarising ALL the jobs matching your saved search paramaters that have been listed in the last 24 hours. i.e. One email = all the jobs from the last 24 hours.
To change your preferences:
Tick or untick the checkboxes next to any and all of your Saved Searches, make sure to click the 'Save Settings' button immediately below when you are finished.