In German language (kwT) remains reasonably common. "kein weiterer Text" = no further content. Often still duplicated in the body, because people read their messages on all sorts of funny devices / in all sorts of funny clients.

Even better than any such marker: Rearranging so the acronym (e.g. LGTM, NAK, ASAP) or greeting/valediction is the last word, ticking off both the formalities and the EOM marker simultaneously.