I deleted every single mail from Mail.app on iOS 8.3 (inbox, sent, trash). However, Mail still occupies 798 MB for "mails and attachments" according to the memory overview. How can I clear this memory?
According to OS X Daily, you can try removing the account from the mail app and adding it again. Source
Tetsujin is correct, backup the phone, then go into settings -> general -> reset and erase all settings and data. Then restore the phone from the backup you just created. The available space should be better.
One thing I learned a couple of years ago and not sure if it still applies. If you do a hard reset (Sleep and home buttons pressed until the phone reboots) three times in a row, IOS will do some rather intensive cleanup and file system checks after the 3rd reboot. That might help. Not sure but it is quicker than backup/restore and won't hurt a thing.
Go to iTunes and try to buy or rent a movie with more memory needs than your device has available OR just go to TV app and try to download a movie you already own that is larger than the space you have available. You will be informed you do not have enough memory, and this will clear memory caches, especially email ones, freeing up more memory. This method increased my memory available from 780MB to 2GB
You must log in to answer this question.
protected by Community♦ Dec 22 '16 at 12:56
Thank you for your interest in this question.
Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).
Would you like to answer one of these unanswered questions instead?