1 files changed, 6 insertions, 0 deletions
diff --git a/lib/PublicInbox/NNTPD.pm b/lib/PublicInbox/NNTPD.pm
index 451f4d41..b8ec84ed 100644
--- a/lib/PublicInbox/NNTPD.pm
+++ b/lib/PublicInbox/NNTPD.pm
@@ -41,6 +41,12 @@ sub refresh_groups () {
                  if (ref $ngname) {
                          warn 'multiple newsgroups not supported: '.
                                  join(', ', @$ngname). "\n";
+                # Newsgroup name needs to be compatible with RFC 3977
+                # wildmat-exact and RFC 3501 (IMAP) ATOM-CHAR.
+                # Leave out a few chars likely to cause problems or conflicts:
+                # '|', '<', '>', ';', '#', '$', '&',
+                } elsif ($ngname =~ m![^A-Za-z0-9/_\.\-\~\@\+\=:]!) {
+                        warn "newsgroup name invalid: `$ngname'\n";
                  } elsif ($ng->nntp_usable) {
                          # Only valid if msgmap and search works
                          $new->{$ngname} = $ng;