Forget passwords - you're using an ANCIENT version of Zimbra. If you care about security you should be upgrading to a newer version (latest in the 7.2.x or 8.x series) as soon as possible.
Originally Posted by ask2me0077
As for blocking connections, you can block anything you want at the firewall level. You'd have to find IP lists of where to block but its like trying to stop a flood, it will never work. Fix your security issues (i.e. using a four year old version of Zimbra). Aside from that, make sure you have spam filtering in place to limit the number of phishing emails that come in to your users, educate them about clicking on fraudulent links and giving out their username/password.
State University of New York at New Paltz