Calvin_BT Said:
"Mail Not downloaded from server I want to open mails in Mails App, but all of the inbox shows nothing when I want to view a mail. All in the mail only shown: This message has not been downloaded from the server. What happened? My internet connection was fine."
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Use a New App Password:
Do you use an App Password? If so, try a new App Password. Sometimes, changes (i.e. updates) are made to the iPad, and then mail server syncing becomes an issue (which is what a new App Password it intended to fix). For example, go here for gmail: Sign in with App Passwords - Google Account Help - Google