OK it was my fault in the first place for ignorance/indiscipline, for many years I never deleted an e-mail. I got up to about 25,000 mails, then thought I should do something about it. (In fact I was advised to not update my Mac OS till I did). I deleted about 10,000. I don't want to do it indiscriminately, always want to be sure of not deleting anything I want to keep, so a bit slow. I have though this situation - there remain 15,000 mails on my Mac but 17,000 on my I-pad. My best inference is that the two devices have communicated somewhat but not completely. I don't want to have to do the job twice. It has been much easier to delete on the Mac than the iPad - on the Mac I can highlight 300 posts, e.g. all those from one journal, and delete the block - I haven't found a way to delete more than one mail at a time on the iPad. Stuff on the web about this is either above my head or out of date. (Or gives instructions about things that don't exist like a Tools Tab I don't think my Mac has.) However I found on my Mac under Mail, Mailbox, the option 'Synchronise - hotmail, which sounds promising for what I am trying to do. Why don't I just try it? Because what will it do if it finds a mail in one box and not the other? Will it delete the unwanted one or will it restore it where it was deleted? I don't want to see any of those maybe 2,000 or more deleted mails again! Maybe related, Bluetooth on one device recognises I have the other. Gives me an option to connect them somehow. Would putting them into this kind of communion be relevant to what I'm trying to do? If not what is it good for?