$hdr->header_set('X-Alt-Message-ID', @alt);
}
- # clobber some
+ # clobber some existing headers
my $ibx = $smsg->{-ibx};
my $xref = xref($smsg->{nntp}, $ibx, $smsg->{num}, $mid);
$hdr->header_set('Xref', $xref);
- $xref =~ s/:[0-9]+//g;
- $hdr->header_set('Newsgroups', (split(/ /, $xref, 2))[1]);
+
+ # RFC 5536 3.1.4
+ my $newsgroups = (split(/ /, $xref, 2))[1]; # drop server name
+ $newsgroups =~ s/:[0-9]+\b//g; # drop NNTP article numbers
+ $newsgroups =~ tr/ /,/;
+ $hdr->header_set('Newsgroups', $newsgroups);
+
header_append($hdr, 'List-Post', "<mailto:$ibx->{-primary_address}>");
if (my $url = $ibx->base_url) {
$mid = mid_escape($mid);