Which certificates do I need for a new laptop?

Today I have faced an issue with my daughter’s new MBP. On her previous machine I had security certifications from Comodo installed so we could have digitally signed and encrypted emails sent. Since we got her new MBP and migrated some system data from a Time Machine backup, the certificates are no longer recognised. I have deleted the certificates and reinstalled them with no success. Cedric Richardet System Migration from a Time Machine backup will copy across passwords in the Keychain, but it won’t migrate certificates properly because these are machine specific. You need to open Keychain Access on the old laptop, select the certificates and choose File > Export. You can save the exported file to a USB drive or attach it to an email. Then on the new MacBook Pro, double-click the certificate file and Keychain Access will ask if you want to add it. This assumes you still have access to both laptops. If the old one has already been reformatted and sold – or has died completely – you’ll need to revoke the certificates and apply for a new set. You can do this by submitting a support ticket to Comodo at support.comodo.com.