Hello there, Without the information requested in my first/previous response, I can only give you a general answer, but I hope this helps.
It is possible that your phone's storage is getting full. So you need to delete unwanted apps, games, music, movies, photos, videos, etc.
Open the Gallery app, and delete unwanted photos and videos. Then tap the Menu, tap Recycle Bin or Trash and also delete the photos/videos there.
Then uninstall unwanted apps. This will make enough space on your Galaxy, so you can send and receive emails without that error.
Please let me know if that didn't work, so I will continue to help you until we fix the problem
Note: This is not my final answer. I strive to provide Excellent service or 5-star service. If you feel you've received anything less or if you are not satisfied or if my solutions didn't work, please don't rate the answer bad or poor or anything and instead let me know by replying here and I will stay with you and try my best to help you until you are fully satisfied or the issue is resolved.