If you find you cannot connect to your mailserver, cannot receive and/or send email, or get an error from your email client during the IP renumbering transition, do the following:
1. Run your domain through http://www.secureweburl.com/account/iplookup.cgi to obtain your new IP.
2. Go into the Account Settings for your email account and change the incoming POP3 and the outgoing SMTP server address to the new IP. Leave this setting in place for the next several days. You can then change it back to mail.yourdomain.com.