This post was imported from an old blog archive, and predates the creation of AdamCaudill.com.
This is another code example made by request for a forum member, it simply retrieves the default value from HKEY_CLASSES_ROOT\mailto\shell\open\command which should be the default mail client.
Option Explicit
Private Declare Function RegOpenKey Lib "advapi32.dll" Alias "RegOpenKeyA" ( _
ByVal hKey As Long, _
ByVal lpSubKey As String, _
phkResult As Long _
) As Long
Private Declare Function RegQueryValueEx Lib "advapi32.dll" Alias "RegQueryValueExA" ( _
ByVal hKey As Long, _
ByVal lpValueName As String, _
ByVal lpReserved As Long, _
lpType As Long, _
lpData As Any, _
lpcbData As Long _
) As Long
Private Declare Function RegCloseKey Lib "advapi32.dll" ( _
ByVal hKey As Long _
) As Long
Private Const REG_SZ = 1
Private Const ERROR_SUCCESS = 0&
Private Const HKEY_CLASSES_ROOT = &H80000000
Public Function GetDefaultMailClient() As String
Dim lngResult As Long
Dim lngKeyHandle As Long
Dim lngValueType As Long
Dim lngBufferSize As Long
Dim strBuffer As String
lngResult = RegOpenKey(HKEY_CLASSES_ROOT, "mailto\shell\open\command", lngKeyHandle)
lngResult = RegQueryValueEx(lngKeyHandle, "", 0, lngValueType, ByVal 0, lngBufferSize)
If lngValueType = REG_SZ Then
strBuffer = String(lngBufferSize, " ")
lngResult = RegQueryValueEx(lngKeyHandle, "", 0, 0, ByVal strBuffer, lngBufferSize)
If lngResult = ERROR_SUCCESS Then
If (InStr(strBuffer, Chr$(0))) > 0 Then
GetDefaultMailClient = Left(strBuffer, (InStr(strBuffer, Chr$(0))) - 1)
Else
GetDefaultMailClient = strBuffer
End If
End If
End If
End Function
