SYMPTOMS
The following error message is displayed upon logging into Webmail:Your Internet Address has changed since the beginning of your Mail session. To protect your security, you must login again.
RESOLUTION
It means that Horde is accessed via an ISP that has dynamic proxies. The only solution is to turn the 'checkip' feature off in Horde.To do this , the following file needs editing: "%plesk_vhosts%\webmail\horde\config\conf.php".
These two lines:
$conf['auth']['checkip'] = true;
should be changed:
$conf['auth']['checkip'] = false;
in order to switch IP address checking off upon logging into Webmail.