When searching using the stock Mail app, if a search term wasn't in the list of my currently synced emails, it would then continue the search on the server. It was really good for only syncing 3 months worth of emails but if I needed something from a year ago it would search the server.
tThe problem is I don't use it often so I can't remember the last time I used it and if this was available in iOS12 or is it broken in iOS13?
tThe problem is I don't use it often so I can't remember the last time I used it and if this was available in iOS12 or is it broken in iOS13?