I have Mediatek Smartphone with stock Android 7.0 and suddenly it increases data usage. Tracked it down to /data/data/com.android.email/cache which is occupying 1.6 GB. I have cleared cache many times which maybe explains the massive data usage 38 GB this month. The question is why it happens just now and not the months before?
How can i prevent increasing cache?
Edit: I use the stock email app for about 1 year without problems. I have 2x IMAP accounts connected. Recently I updated security patches to latest available Dec 2018 _V22. But after firmware update the battery drain increases too fast, so I decided to revert back to May 2018 CUBOT_KING_KONG_7081C_V16_20180517 (both still 7.0, no updates 7.1.2 available).
The phone is rooted so I can see that it downloades many files body1009174325.tmp in cache folder each with size 44,76 KB. I have inspected this file and it turns out it is a corrupt PDF which is downloaded a million times again and again. I found the responsible email and the App says attachment download has failed. After I pressed "save" the attachment was successful downloaded. After I cleared cache, the tmp files are gone. Now it starts repeating with next message (different tmp files, all the same). This time it is not a PDF and its hard to find the related email.
How can I avoid this behavior?