When i open my outlook emailaccount on my ipad i see a lot of small icons of emails

Meet the “Shelf” - this being a new function of the iPadOS15 multitasking environment.

iPadOS permits you to have multiple “instances” of the same App - each instance being self contained. The shelf, when visible, shows a thumbnail of each running instance of an App.

The Mail Shelf, that you illustrate, will show each of your currently open email messages or email draft messages. Tapping a thumbnail immediately switches your view to the specific App instance or message; individual views can be closed/dismissed (if desired) by swiping the related thumbnail off the top of the screen.

The iPadOS multitasking environment permits you to run multiple “instances” of the same App, such as Mail - with each instance, perhaps having a different open inbox.

By example, if you have three running instances of Mail, the Shelf will show a thumbnail corresponding to each running instance of Mail. Simply tapping a thumbnail will switch directly to that running instance of the Mail App. 

This article from Appleinsider has a useful explanation of this new feature along with many of the updates to multitasking:

https://appleinsider.com/articles/21/08/12/how-to-master-multitasking-on-ipad-and-ipad-pro-in-ipados-15

The iPad User Guide is also a rich source of frequently overlooked information. The Guide is available both online using a web browser (such as Safari), or as an Apple Books download:

iPad User Guide - Apple Support

https://books.apple.com/book/id1567104892