Q: Mail on my iPad is erasing my emails after a few days. How can I get it to stop doing that?

Is it erasing or not syncing with your email provider after a few days. Go to settings> mail, contacts, calendars> accounts> your email account> mail days to sync> increase lengh of time.

Is it being erased from your email account if you log into your email account using Safari ?

Hi. Are you using POP to receive your mail? Check the settings for the account. It will say POP or IMAP account. If so, this Problems with mail in iOS 9 thread has a lot on discussion on this. It seemed as if Mail assumed all accounts were using IMAP, so it could freely erase local copies to save storage, because they could always be recalled from the server. It seemed to especially affect larger messages. My solution was to switch to AltaMail, which works reliably.