Gmail is one of the most popular web mail service from Google and they have been adding more and more features to the email to make it more productive and better. Although there is search in most of the email services, searching emails based on file size, date etc are not possible. Gmail has now added new advanced search operators which help you search emails better. Advanced search operators are query words or symbols that perform special actions in Gmail search. These operators allow you to find what you’re looking for quickly and accurately.
For example, to find emails larger than 5MB, you can search for size:5m or larger:5m or to find emails sent over a year ago, older_than:1y.
Here is a list of all search operators for Gmail.