Hi,
Now you can revoke Comodo secure email certificate using the revocation password while you apply email certificate .
For this use the links
https://secure.comodo.com/products/!SecureEmailCertificate_Revoke
https://support.comodo.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=1293&nav=0,96,32