iCloud 
Check available email storage
Your iCloud account includes 5 GB of free storage for your mail, documents, account information, and the iOS settings and app data that are automatically backed up to iCloud.
If necessary, you can manage your iCloud storage or upgrade your storage.
See how much space is available
On your iOS device, go to Settings > iCloud, then tap Storage & Backup.
On your Mac, open iCloud preferences, then click Manage.
On your Windows computer, open the iCloud Control Panel, then click Manage.
For more information, see the Apple Support article iCloud: Troubleshooting storage issues.