We are using Exchange 2003 v6.5.7638.1 on a W2K3 SP2 server. We have a Barracuda 300 SPAM filter that monitors incoming and outgoing email. We have users who now have not been able to send group emails that they were able to send a few days ago. We were hit with a virus that affected emails - which we resolved- but this seems to be the only change that we can see that would possibly affect emails. We checked with our ISP and Barracuda support and both confirmed we are not on any blacklist that would prevent these emails from being sent. We can send to these domains with a single recipient, but with multiple recipient emails to these domains (Aol.com, Yahoo.com, Gmail.com, for example) we are now unsuccessful. I am watching the queue in Exchange and they just sit there and retry. Our Barracuda is not blocking these emails. Any suggestions would be greatly appreciated.