Recertify expired Notes certificates

In Notes 4.6, the certificates of all users have been expired; no backup is available. I changed the system date to 2 months back and tried to recertify. It gets certified, but when I'm trying to open the mail file, it says, "you are not authorized to open the database." Is there another way to recertify the expired certificates?

As long as your administrator certificate hasn't expired, you can recertify the individual ID files if you have them on your machine. That is the only way to recertify users who have gone past their expiration without sending you their recertify requests.