Clearing the cache is a safe way to free space on your device and give BlueMail a fresh copy of your mail. Your emails live on your provider's server, so anything cleared locally comes straight back on the next sync.
Go to Settings | Global Settings | Advanced Features | Clear Cache. It is the last item on that screen.
BlueMail asks you to confirm first, and tells you exactly what will happen:
Clearing the cache will re-download the last 14 days of emails based on your sync settings. Your account settings will not change. Do you want to continue?
Tap through and you will see Cache cleared successfully! Your accounts, passwords, signatures and preferences are all left as they were.
How Much Comes Back
How far back BlueMail re-downloads is your choice, set by your Days to Sync preference. Raise it to keep more mail available offline, or lower it to keep the app lean. See Offline Storage and Days to Sync.
See the Space First
If you would like to know how much you will actually reclaim, the Storage usage screen shows what BlueMail is holding, broken down by emails, photos, videos and documents, with a Clear Cache button that displays the figure in GB. See How much storage is BlueMail using?.
