Previously, users could send IBM Notes Traveler S/MIME signed non-encrypted mail to BlackBerry 10.1.x devices without any difficulty. However, after upgrading to BlackBerry OS version 10.2.x, they will now find that this mail cannot be opened.

BlackBerry 10.2.x devices are not able to open S/MIME mail because the value of the MessageClass property sent by IBM Notes Traveler is not one of the S/MIME MessageClass values.
In 10.2, BlackBerry added support for Domino signed and/or encrypted mail. BlackBerry refers to this as "Notes Native Encryption."

IBM Notes Traveler sets the MessageClass to a certain IPM value for all signed mail. After 10.2.x, BlackBerry tries to open any mail with this MessageClass value as Domino Signed mail.

IBM compared the sync requests sent from IBM Notes Traveler to both 10.1.x devices and 10.2.x devices and, in both cases, the IBM Notes Traveler server sends the same IPM value.
Therefore, it appears the only reason users were previously able to open S/MIME (non-encrypted mail) with BlackBerry OS 10.1 was because the device ignored the particular MessageClass value sent by IBM Notes Traveler. Now, the device can no longer ignore this value and still support Domino Encrypted/Signed mail, as introduced in BlackBerry OS 10.2.x versions.

IBM Notes Traveler does not support S/MIME mail and therefore does not utilize any of the MessageClass values for S/MIME per the specification. When attempting to sync or read S/MIME mail on ActiveSync devices the results may be unpredictable.

IBM's investigation continues with the intention to establish whether there are any viable options to resolve this issue other than providing full S/MIME support with IBM Notes Traveler. S/MIME support is also a possibility for future releases, and the feature request is currently documented within IBM.