my $eml = PublicInbox::Eml->new($mref);
[ 200, res_hdr($ctx, $eml->header_str('Subject')),
[ msg_hdr($ctx, $eml, $ctx->{mid}) . msg_body($eml) ] ]
my $eml = PublicInbox::Eml->new($mref);
[ 200, res_hdr($ctx, $eml->header_str('Subject')),
[ msg_hdr($ctx, $eml, $ctx->{mid}) . msg_body($eml) ] ]