I'm running IOS 10.2.1 on my iPhone 6S. My Mail storage usage continues to slowly increase regardless of how I try to reduce it. I run 2 POP3 accounts and religiously delete mail, attachments, etc. But somehow my Mail storage slowly increases up to now 1.25 GB. The only way I've been able to clear the storage is to delete an account and re-add it. That seems pretty lame for such a sophisticated device. What am I missing here?