Sender ID:
In order to avoid filtering, all messages to MTS Serbia (22003) with a numeric Sender ID will be replaced by "NXSMS".
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