Anyone else notice unexpected background activity on the Mail client? I happened to be looking at the battery usage on my iPad and noticed the mail client had spent x% in the background. As I have my email accounts set up just to manually retrieve my mail I.e. when I go into the mail app and swipe down to retrieve new mail, I wouldn't have expected much, if indeed any background activity at all. Might this suggest a garbage or memory clearing task that wasn't there prior to iOS 9? Prior to that release, it was evident that the mail client really didn't handle deletions all that well - even with supposedly emptied inboxes, I still ran up 100s of Mb of mail storage usage which I could only release by deleting and recreating mail accounts.
(As an aside, I went into my local Apple Store today and had the expected frustrating "we don't know about such an issue, so it must be your ISP/ delete and recreate your account/ use IMAP, you can still access all your mail in flight mode"/ and best(?) of all when I referred to this thread - the impertinent response that "you can't believe everything you read on the Internet". I did manage to elicit a call from support tomorrow, but given my experience in-store, I'm not expecting much better)