Hello,

I need to send S/MIME encrypted emails, but the recipient cannot open them.  Working with certificate vendor Entrust Datacard they are saying the following:

"After further investigation of the email header,  we came to the conclusion that your email security appliance “Cisco Ironport” alters the email content in such a way that your certificate signature (that contains the hash of the message) becomes invalid. Hence your emails are not trusted on the recipient end."

Is there a way to bypass spam filtering on outbound messages?   Is anyone able to send out S/MIME encrypted messages with Outlook 2016?  

Thank You