Thunderbird was sending and receiving just fine until a couple hours ago. Now, I cannot send anything to anyone - including my email provider. The message is: "Outgoing server (SMTP) error. The server responded: (C18) RBL restriction: Blacklisted by Internal Reputation Service" I verified all the settings (though I changed nothing prior to the problem) and all is correct. I've checked with tech' support and they verified that my address does not have a Blacklist. I've restarted the program and restarted the computer. I've also donated several times to Thunderbird. Before I change clients, I thought I'd see if anyone had a fix for this. Thanks, D