Sender ID:
All Sender IDs to Namibia (MCC=649) are currently being changed to a local shortcode. This is to avoid filtering which is extremely regular in Namibia, and ensure message delivery.
Content:
There are no additional content restrictions beyond those in our Acceptable Use Policy
Other features/restrictions of note:
Delivery Receipts:
Handset delivery receipts are supported.
Links:
Global SMS Features Overview (Outbound only)
Global SMS Numbers Features Overview