Gmail was built so that we don’t have to delete any emails or even need to organize email as its search is powerful enough to find things. But after 16 yrs of use, I have started to stumble on size restrictions. One easy way is to find all big emails and delete them if not required.
To find big emails just type size:30MB in the search box and it will return all emails larger than 30 Megabytes. You can change the “30” to a higher, or lower, number to increase or decrease the number of results. You can change the size to KB if required. eg: ‘size:20KB’.