Teste mal das Bitte.
CSS
.box[data-box-identifier="de.wbb-elite.news.UnreadNews"] {
.htmlContent > :last-child, .messageBody > .messageText > :last-child, .messageSignature > div > :last-child, .redactor-layer > :last-child {
min-height: 200px;
}
.messageList:not(.messageReducedList) > li .message {
border-right: 1px solid rgb(210, 210, 210);
}
}