Native/local ES2ES is currently only for PCs.
For testing on Android, you may use the public LDAP server at
The S/MIME email client MUST support LDAP address books. There are a few out there and hopefully mobile Outlook and default Exchange clients will support address books (like their Desktop versions do) soon. Nine email from 9 Folders does a wonderfully seamless job doing so. On Nine email, once you have S/MIME configured all you need to to is:
Nine LDAP setup summary: Nine Settings->Choose your account
->Server settings/LDAP->LDAP->NEW->Search Base:dc=* 
->Server, Port:389->Save.
Go back to the INBOX and try to send an Encrypted email to
You now have seamless S/MIME across all boundaries.
Note: Android apps will not honor User installed Root CAs so you must be using real S/MIME certificates or get your certificate into the Trusted store somehow.

Step by Step Nine email setup and sending example

Open Nine App

Tap upper left

Tap Settings gear (lower right)

Select account

Scroll down to Server settings

Tap on LDAP

Tap on LDAP again

Tap on NEW on top bar

Fill out fields like this and tap on SAVE

You should have this. Use phone back button to return to Inbox screen.

Tap on lower right "+" to send mew email

Fill in to address. is a good start. Tap on upper right to bring up menu

Scroll down and check Encrypt

To field should turn blue indicating Nine retrieved a certificate for the recipient via ES2ES. Tap the paper airplane to send.

In a minute, notice the auto response. Tap on the Encrypted message to open.