I have been trying to debug the issue I'm seeing for the last 2 days. It seems I've narrowed down the issue to Zimbra Backend. Here's the issue.
I have Zimbra 8.0.3, Z-Push 2.0.8, Zimbra Backend 56.1. I have an iPad and iPhone both syncing with Zimbra well with push. I have installed digital signatures on the iPad and iPhone from StartSSL and Comodo. If I send an email using the Exchange configuration that connects to z-Push/Zimbra that is signed and encrypted - it passed through and works fine. However, if I send an email through z-Push and Zimbra that is just signed, it is received as an empty email with an smime.p7s attachment that is unreadable.
However, if I set up an account on my iPad and iPhone that sends the same email to zimbra with an IMAP/SMTP setup, it the message arrives perfectly as just signed with no attachment.
The configuration on the iPad/iPhone seems to be working fine but the intermediate z-push/zimbra backend seems to be unable to properly encode the signed email (not encrypted). However it does properly encode the signed and encoded S/MIME email.
As I stated in the previous ticket you opened, I have no idea about S/MIME and signing emails on the client.
That said, if you can send me a complete debug log file, and I will take a look to see if I can help you.
Click through to my profile page and click the "Send me a message" link. Include in it a valid email address for yourself. I will reply with my email address where you can send the debug log file.
https://sourceforge.net/users/liverpoolfcfan/profile/
Can you please confirm you received an email from me
The fix for this issue has been checked into the source Code as Release 56.2
It will be released in the next release - Release 57
Closing ticket