Today, we are excited to announce the availability of OWA for iPhone and OWA for iPad, which provides even more value to organizations on any Office 365 subscription that includes Exchange Online. ...
Updated Jul 01, 2019
Version 2.0
Blog Post
Sunith Mandalia,
Official requirements require an iPhone 4S or higher or iPad 2 and higher, not sure where you got the idea that it can be installed on an iPod :)
https://itunes.apple.com/us/app/owa-for-iphone/id659503543
Requirements: Compatible with iPhone 4S, iPhone 5, iPad (3rd generation), iPad Wi-Fi + 4G, iPad (4th generation), iPad Wi-Fi + Cellular (4th generation), iPad mini and iPad mini Wi-Fi + Cellular. Requires iOS 6.0 or later. This app is optimized for iPhone
5.
https://itunes.apple.com/us/app/owa-for-ipad/id659524331
Requirements: Compatible with iPad 2 Wi-Fi, iPad 2 Wi-Fi + 3G, iPad (3rd generation), iPad Wi-Fi + 4G, iPad (4th generation), iPad Wi-Fi + Cellular (4th generation), iPad mini and iPad mini Wi-Fi + Cellular. Requires iOS 6.0 or later.