With BlueMail you can set the polling time by following these steps: Tap More... | Notifications | Instant Push Settings | Push or Fetch | Choose Fetch | Fetch Interval and choose how often you wish to check for new emails.
On iOS
With BlueMail you can set the polling time by following these steps: Tap Settings | Notifications | Choose an account | Instant Push Settings | Push or Fetch | Choose Fetch | Fetch Interval and choose how often you wish to check for new emails.