1'a@b@c@d' quoted '"a@b@c"@d' 2'a@b@c@d' quoted flags=8bitclean|bare_localpart '"a@b@c@d"' 3'"a@b@c"@d' unquoted 'a@b@c@d' 4'"a@b@c"' unquoted 'a@b@c' 5'"a@b@c"@d@e' unquoted 'a@b@c@d@e' 6'' quoted '""' 7