+sub xref_by_tc ($$$) {
+ my ($xref, $pi_cfg, $smsg) = @_;
+ my $by_addr = $pi_cfg->{-by_addr};
+ my $mid = $smsg->{mid};
+ for my $f (qw(to cc)) {
+ my @ibxs = map {
+ $by_addr->{lc($_)} // ()
+ } (PublicInbox::Address::emails($smsg->{$f} // ''));
+ for my $ibx (@ibxs) {
+ my $ngname = $ibx->{newsgroup} // next;
+ next if defined $xref->{$ngname};
+ $xref->{$ngname} = eval { $ibx->mm->num_for($mid) };
+ }
+ }
+}
+