I get an email certificate warning when setting up email accounts to use secure protocls

Email & Webmail
You may receive an Internet Security Warning that says:
"The server you are connected to is using a security certificate that cannot be verified"
"The target principal name is incorrect"
if you are using Outlook as your email client.  You may receive similar messages when using other email clients or smartphones.
This is because you are using an email server name that does not match the actual name of the email server. 
Our servers allow connection via mail.<yourdomain>
For convenience, you can use an address for connecting to our email servers that is different from the actual name of the email server.  For instance, you can use mail.<yourdomain> as the name of the email server that handles the emails for your domain.
This is a legitimate (and useful) naming convention for domain owners, but it can cause certificate warnings to be displayed when attempting to use secure email protocols.
The email server name must match the name on the SSL Certificate
We operate a number of email servers, and each email server has a specific name that it uses when connecting to other email servers to send and receive emails.  For secure certificates to work, the name on SSL (secure) Certificate must match the actual name of the email server. 
The actual (real) name of the email server handling emails for your domain may be different from the name you are used to.
All of our email servers use the following domains and naming conventions:
<name>.nsnetwork.net, or
<name>.rackdns.net, or
<name>.rackteam.com, or
The actual/real name of the email server being used by your domain is available in the Control Panel, but if you are not sure where to look please contact our support team and they will be able to provide it to you - don't forget to tell them what your domain is!
How to I stop the warning?
If you change the POP and SMTP server addresses your email client is using to be the same name as the actual email server, the error will no longer be shown.
Alternatively, you can elect to ignore the error.   If you do this your communications will still be encrypted but you should only accepted/override the security warning if you are absolutely sure you are connecting to the correct server for your domain.