It's the “signature” (free text, but people use it for information, address, phone number, disclaimers and what not). It appears under the “tearline”, that consists of two dashes and a space (“-- ”).

On unix OSes it lives as the file ~/.signature, and many email clients will insert the contents of that file under the tearline in outgoing emails. E.g.: https://www.gnu.org/software/emacs/manual/html_node/emacs/Ma...