If you are a System Administrator for your Organization's Salesforce Instance, you may have or may receive an email notification that warns you that the SFDC Certificate has or will expire soon.
You do not need to do anything about this email.
The certificate that is referenced is one that is installed so that you can use SSO (Single Sign-On) and easily go from COACH to SHARE (or vice versa) without having to log into both platforms. This is a common notification that Salesforce send out before it expires. Although the certificate will expire a year after it was installed, you should still be able to use SSO when going from one platform to the other. You may receive this email sixty (60), thirty (30), ten (10), and/or the day before the expiration date.