[MM3-users] Too Many From Headers

I am getting mail bounced from yahoo and gmail smtp servers with this message:

554: Message not accepted due to failed RFC compliance. Too many From headers. See https://senders.yahooinc.com/smtp-error-codes#rfc-compliance-failures

What would cause mailman to build too many from headers when distributing email? It appears the from address is repeated 5 times in the from field. I'm guessing it is something in my configuration but what and where?