There are already some posts about this but they're old. This started occurring with Yahoo mail today only after I upgraded to the latest version of ZD. It occurs whenever I try to send an email. If I log into my Yahoo account online through a browser and send, I get stopped by the dreaded "Captcha". So that's the problem. No way Zimbra can deal with that accursed hindrance. I don't have anywhere near 100 contacts in my address book and I am only sending to one address each time, not spamming. So why is Yahoo doing this and is there any work-around? I am able to send with other Yahoo accounts using ZD. Only this one account is being blocked.