The underlying problem seems to be the one described in https://bugs.kde.org/show_bug.cgi?id=404990
The workaround mentioned in its 2nd comment, using PLAIN authentication method, fixes the problem.
The problem has nothing to do with KDE Wallet unlike the very misleading Kmail error -- that's why I'm not marking this bug as a duplicate.
The underlying problem seems to be the one described in https:/ /bugs.kde. org/show_ bug.cgi? id=404990
The workaround mentioned in its 2nd comment, using PLAIN authentication method, fixes the problem.
The problem has nothing to do with KDE Wallet unlike the very misleading Kmail error -- that's why I'm not marking this bug as a duplicate.