How do I delete outdated S/MIME certificates in my iphone 5s
I have the following problem with my iPhone 5S (iOS 8.1.2):
I am using S/MIME for email encryption. Therefore I have cerfiicates installed for certain receiver email addresses.
Some of those certificates are expired. But it is impossible to install a new valid certificate. The iPhone email application continues to use the old certificate (public key) of the receiver for encrypting the emails.
How can I delete the outdated certificates?
I already reset the iPhone to factory settings and restored from backup. However the certificates appear to be saved in the backup as well.
iPhone 5s, iOS 8.1.2, S/MIME, certificates