JS

let pat = new RegExp(/\b([\w.]+)@([\w.]+)\.(\w+)\b/, "gm");
let occs = new Set(input.match(pat).sort());
console.log([...occs].join(";"));

\b <--- start and end of a "word" (or email) ---> \b

\w = [a-zA-Z_]

[\w.] : We don't need to scape dots inside those brackets.