Here are the steps I followed to prevent the tracker email notification sent to a SourceForge mailing list address from being held for moderation.

1. Navigate to Mailman admin > Privacy options > Sender filters. Then add noreply@sourceforge.net to the list of non-member addresses whose postings should be automatically accepted.
2. Navigate to Mailman admin > Privacy options > Recepient filters. Then add noreply@sourceforge.net to alias names (regexps) which qualify as explicit to or cc destination names for this list.

The first step was necessary because all emails sent by tracker has noreply@sourceforge.net as the From address.

The second step was necessary because all emails sent by tracker has noreply@sourceforge.net as the To address.