This is an ack for client SMS request sent via 
SNAC(15,02)/07D0/1482. It contain xml string with data. There are three ack 
types: message_deliverable, message_smtp_deliverable, message_undeliverable. Here 
is the format of snac/xml:
  
|  00 15 | 
  | 
word | 
  | 
SNAC family | 
 
|  00 03 | 
  | 
word | 
  | 
SNAC subtype | 
 
|  00 00 | 
  | 
word | 
  | 
SNAC flags | 
 
|  xx xx xx xx | 
  | 
dword | 
  | 
SNAC request-id | 
 
 
 |  
 |  
|   | 
|  00 01 | 
  | 
word | 
  | 
TLV.Type(1) - encapsulated META_DATA | 
 
|  xx xx | 
  | 
word | 
  | 
TLV.Length | 
 
 
 |  
 |  
|   | 
|  xx xx | 
  | 
word (LE) | 
  | 
data chunk size (TLV.Length-2) | 
 
|  xx xx xx xx | 
  | 
dword (LE) | 
  | 
request owner uin | 
 
|  DA 07 | 
  | 
word (LE) | 
  | 
cmd: META_DATA | 
 
|  02 00 | 
  | 
word (LE) | 
  | 
request sequence number | 
 
|  96 00 | 
  | 
word (LE) | 
  | 
subcmd: META_SMS_RECEIPT | 
 
 
 |  
|  0A | 
  | 
char | 
  | 
success byte | 
 
|  00 01 | 
  | 
word | 
  | 
unknown field | 
 
|  00 0d | 
  | 
word | 
  | 
unknown field | 
 
|  00 0b | 
  | 
word | 
  | 
unknown field | 
 
 |  
|  xx xx | 
  | 
word | 
  | 
xml data strlen | 
 
|  xx .. | 
  | 
ascii str | 
  | 
xml data string | 
 
 
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