Comodo certificate not verified, unable to send encrypted emails

I created a free SSL certificate for email on Comodo's website. I installed the cert on my Windows machine and can send digitally signed and encrypted emails via S/MIME from Outlook. I exported the certificate as a PFX file and emailed it to myself so that I can install it on my iPhone (IOS 9.02). It installs the certificate, but it says it is Not Verified. I believe because of this, I am unable to send encrypted emails via IOS. It says that it is unable to send signed messages because the signing identity for my email address can't be found. When I go to Advanced settings in the email account, I can see the certificate is selected and it says it is trusted.