Q: iPad air ios8 deletes mail in inbox every few days.

see if bobseufert's illustration helps > Re: e-mail disappear on my iPad without me deleting - ÇÇÇ

Puzzling as to how the new got to be IMAP, unless you chose that when setting up the account

Using old as a model, delete account on new and redo it as POP

IMAP is determined by the provider's system. Even more puzzling how IMAP was retrieving POP account mail at all.

have you reset? restore? I am out of suggestions as I cannot recreate to test your issue. respond and I will help keep this "alive" from time to time - ÇÇÇ

Some where along the lne the Mail app changed from hom many emails you could keep to the lenght of sync, it's been this way at least since IOS 6. It's normal, to free up room on your iPad. Remember just because a email auto-deletes it's not gone, it's just not on your iPad. You can go to your email account onlne to see how many email you have. You can also use the search field if you also know the name. if you live near an Apple Store it might be a good time to stop in and find out why you don't have the option to change the sync amount.

I think that's the best course of action. Sometimes nothing beats hands on help. When they get the problem solved please post back with the solution. Thank you.

Hopefully they'll have the answer. Please don't forget to post back with the solution. Thank you.

Use the email app from the AppStore instead of the stock app. Like gmail or whatever you use.