No longer able to access bigpond emails

Hello Neenie_N,

It sounds like you are using the Mail app with your Big Pond email account setup but the app seems to close on its own when you open it. What I would do first is quit the Mail app:

Force an app to close in iOS

1. Press the Home button two times quickly. You'll see small previews of your recently used apps.
2. Swipe left to find the app you want to close.
3. Swipe up on the app's preview to close it.

When you have done that restart the device and test the issue again:

iOS: Turning off and on (restarting) and resetting

If the issue persists and it is an IMAP account I would next remove the account, repeat the above steps and then try again:

Remove the affected email account from your device with these steps:

1. Tap Settings > Mail, Contacts, Calendars.
2. Tap the email account.
3. Tap Delete Account.
4. Add your account again.

Get help with Mail on iPhone, iPad, and iPod touch

Thank you for using Apple Support Communities.

Thanks for the update! Next I would backup your device to iTunes, then restore it as new and verify that it works and you can access your Mail account again:

How to erase your iOS device and then set it up as a new device or restore it from backups

If it does, then restore your backup to either verify it still works and the software just needed reinstalled, or isolate the issue to the backup file itself.

Yay! You're quite welcome and Happy New Year to you too!