Both IMAP and POP3 mailboxes will store downloaded email messages on your iPad. The older POP3 mail protocol could be configured to either:
- Download and leave a copy on the Server
- Download and delete from the Server
If mail was deleted from the server when downloaded, the only copy of the mail message will reside on the device until manually deleted; after deletion, the associated message(s) cannot be recovered or re-downloaded.
Unless you only have basic BT Mail, you will be able to access your BT Mail using either IMAP or POP3; when adding a mail account to your iPad using the Add Mail wizard, the default configuration for many Mail Providers (including BT Mail) will be IMAP; if using POP3/POP3S, the account must be manually configured - providing all the server/port connection details for the POP and SMTP server settings.
Start with initial fault finding:
What happens when you try to receive or send email? Do you see any errors - and if so, what do you see?
If email is failing to send or receive, you are likely to see indicative errors at the bottom of the mail sidebar - the wording of the error usually providing sufficient information to determine the nature of the problem.
Deleting and re-adding your email account is sometimes the easiest way to resolve a problem with a specific Mail account. After deleting the account, perform a forced restart before re-adding the email account to your iPad.
Settings > Mail > Accounts > [Your Mail Account] > Delete Account
Force restart iPad - Apple Support
Settings > Mail > Add Account
Add an email account to your iPhone or iPad – Apple Support (UK)