Certificate Popup error in Microsoft Outlook sending emails

To resolve this problem, you must install a certificate that is not a self-signed certificate on the Exchange 2010 server that hosts the Client Access Server role. This certificate can be either one that a Certification Authority server in your organization issues or one that a third-party certification authority issues.

If you cannot install a certificate that is not self-signed on the Exchange 2010 server, you can use the following workaround on workstations on which Outlook is installed. These steps install the self-signed certificate from the Exchange 2010 server into the Trusted Root Certification Authority store on the workstation. To do this, follow these steps:

1. 1. Start Outlook.

1. 1. In the Security Alert dialog box, click View Certificate. 

1. 1. In the following View Certificate dialog box, click Install Certificate.
      
      
      

1. 1. In the Certificate Import Wizard, follow these steps:
      
      
      1. 1. On the following Certificate Store wizard page, click Place all certificates in the following store, and then click Browse.
            
            
      
      
      1. 1. In the following Certificate Store dialog box, click Trusted Root Certification Authority, and then click OK.
            
            
            
      
      
      1. 1. On the Certificate Store wizard page, click Next.
      
      
      1. 1. Click Finish to complete the wizard. 
      
      
      1. 1. Click Yes as the following screen shot shows when you are prompted to confirm the installation of the certificate.
            
            
            
      
      
      1. 1. Click OK when you are advised that the import was successful. 
      
      
      1. 1. Click OK to close the View Certificate dialog box. 
      
      
      1. 1. Click Yes in the Security Alert dialog box to continue to start Outlook. 
      
      
      1. 1. Exit and restart Outlook.
            
            Now, you do not receive the security warning when you start Outlook.

After you install the certificate by using this procedure, you can confirm that the certificate is installed correctly on the client. To do this, follow these steps:

1. 1. Start Windows Internet Explorer. 

1. 1. On the Tools menu, click Internet Options. 

1. 1. On the Content tab, click Certificates. 

1. 1. In the Certificates dialog box, click the Trusted Root Certification Authorities tab. 

1. 1. Scroll down the list of installed certificates to locate the certificate for your server. (The screen shot for this step is listed below).
      
      
      
      Note In the following scenario where you are using a self-signed certificate on your Exchange 2010 server, Outlook does not display the Security Alert dialog box if both of the following conditions are true: 

• • The certificate is listed.

• • The date in the Expiration Date column has not been reached.