You need a rule and a script. The rule is used to process incoming messages to identify the particular message and then run the script 'SendSMS'. Put the following code in a new module and associate the script with the rule. Change the web address to the valid web address.
Code:
Option Explicit
Private pWebAddress As String
#If Win64 Then
Public Declare PtrSafe Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, _
ByVal lpOperation As String, ByVal lpFile As String, _
ByVal lpParameters As String, ByVal lpDirectory As String, _
ByVal nShowCmd As Long) As Long
#Else
Public Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" (ByVal hwnd As Long, _
ByVal lpOperation As String, ByVal lpFile As String, _
ByVal lpParameters As String, ByVal lpDirectory As String, _
ByVal nShowCmd As Long) As Long
#End If
Public Sub NewShell(cmdLine As String, lngWindowHndl As Long)
ShellExecute lngWindowHndl, "open", cmdLine, "", "", 1
lbl_Exit:
Exit Sub
End Sub
Public Sub SendSMS(oItem As MailItem)
pWebAddress = "http://smsxxxxx.info/?user=username&password=password&PhoneNumber=919840098400&Text=TestSMS&Sender=Tester"
Call NewShell(pWebAddress, 3)
lbl_Exit:
Exit Sub
End Sub