IOS App freezes

I use the app on my iPhone and connect to a Microsoft Exchange on-premise server. The app is syncing mail, but when using the app it freezes quite often. For example swiping a mail to delete it freezes the app for approx 50sec, alternatively and I can restart it.

The same applies to “swipe down” to check whether there are new messages in the mailbox. Here too, the app freezes for approximately 50 seconds.

App Version is 10.2.1465 (34cd093)
iPhone 15 running iOS 18.3.2

Any suggestions?
Thanks!