Untitled

= Table.AddColumn(#"Parsed Date", "Custom", each let
    IsValidEmail = (input as text) =>
    let
        name = Text.BeforeDelimiter(input,"@",{0,RelativePosition.FromEnd}),
        ext = Text.AfterDelimiter(input,".",{0,RelativePosition.FromEnd}),
        domain = Text.BetweenDelimiters(input,name&"@","."&ext),
        return =
            Text.Length(name) > 0 and
            Text.Length(domain) > 0 and
            Text.Length(ext) > 1 and Text.Length(ext) < 6 and
            name = Text.Select(name, {"a".."z","A".."Z","0".."9","_","-","."}) and
            domain = Text.Select(domain, {"a".."z","A".."Z","0".."9","_","-","."}) and
            ext = Text.Select(ext, {"a".."z","A".."Z"})
    in
        return
in
    IsValidEmail([UserPrincipalName]))