Sign & Encrypt

Not sure what happened;  Everyone used to be able to send an email and choose both “Sign & Encrypted” email to internal Exchange user.    The sender would receive an email that it was  “was cryptographically verified”,  and the recipient user was able to read the email.

Now,  we have to send a separate email, that is “Sign” only.  
1). The receiving user opens up the email.  
2). No acknowledgement is sent back to sender.     
3). Once we know, verbally or if the Receiving user sends an email saying the opened it. 
4). We can then send an encrypted email to the user. 

I am unclear why this happened.  We are on Exchange 2010,  outlook clients 2010 & 2007