When attempting to send email from an Android device, the user receives a message that the attempt has failed:
Unable to sign or encrypt message. Certificate not installed.
This issue occurs when the option to sign all outgoing email has been selected. This feature is used when a user wants to encrypt their email using their own certificate (from their own server). Since they are using hosted servers, they will not be able to use this feature. Also, some users may mistakenly select this option thinking it enables the email signature feature.
To disable it, follow this procedure:
1. On the device, find and tap Settings.
2. From the Settings menu, scroll down to the USER AND BACKUP section and tap Accounts.
3. Tap Microsoft Exchange ActiveSync.
4. Tap Settings.
5. Select the email account.
6. Scroll down and tap More settings.
7. Tap Exchange server settings.
8. Uncheck Sign / Sign All Outgoing Email and tap Done.
9. Test by attempting to send another message.