iOS 13.x with the native iOS mail application and the Sender and Recipient fields contain an umlaut (i.e. ä,ü,ö,...) as used in German or Hungarian

iOS Mail displays names improperly and these characters display as utf-8 encoding

iOS mail does not display the Sender and Recipient fields correctly if they contain only a display name

iOS Mail displays 'No Sender' if an archived message contains only a display name in the sender field. Similarly, iOS Mail displays no recipient data if only the recipient's display name is present.

iPad's Notes app items are archived if Notes integration is enabled in iOS Mail's account settings.

The Notes app on the iPad can be configured to work with iOS Mail. When it is enabled, notes created in the application are stored in a root level folder in the archive, and the folder is called "Notes".

This folder is treated as a normal folder by all other mail clients, but on the iPad the only way to view the content of the folder is by using the Notes application. If you disable this integration in the account settings, old notes are completely removed from the Notes application but they remain in the archive.

Re-enabling Notes integration does not restore the removed items to the Notes application. The only way to view your archived notes is by using Enterprise Vault Search.

iOS Mail does not correctly interpret Exchange system messages

If you connect to an Exchange archive using IMAP access in iOS Mail, it does not correctly interpret Exchange system messages such as non-delivery reports. Such messages are not rendered correctly.

IMAP folder names

IMAP folder names must not exceed 256 characters.