'a@b@c@d' quoted '"a@b@c"@d' 'a@b@c@d' quoted flags=8bitclean|bare_localpart '"a@b@c@d"' '"a@b@c"@d' unquoted 'a@b@c@d' '"a@b@c"' unquoted 'a@b@c' '"a@b@c"@d@e' unquoted 'a@b@c@d@e'