[RESOLVED] Find Default Mail Client?

[Joacim Andersson]

Private Declare Function RegCloseKey Lib "advapi32.dll" ( _
    ByVal hKey As Long _
) As Long
 
Private Declare Function RegOpenKeyEx _
 Lib "advapi32.dll" Alias "RegOpenKeyExA" ( _
    ByVal hKey As Long, _
    ByVal lpSubKey As String, _
    ByVal ulOptions As Long, _
    ByVal samDesired As Long, _
    ByRef 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, _
    ByRef lpType As Long, _
    ByRef lpData As Any, _
    ByRef lpcbData As Long _
) As Long
 
Private Const HKEY_CLASSES_ROOT As Long = &H80000000
Private Const REG_SZ As Long = 1
Private Const KEY_QUERY_VALUE = &H1
Private Const KEY_SET_VALUE = &H2
Private Const KEY_CREATE_SUB_KEY = &H4
Private Const KEY_ENUMERATE_SUB_KEYS = &H8
Private Const KEY_NOTIFY = &H10
Private Const KEY_CREATE_LINK = &H20
Private Const STANDARD_RIGHTS_ALL = &H1F0000
Private Const SYNCHRONIZE = &H100000
Private Const ERROR_SUCCESS As Long = 0&
Private Const KEY_ALL_ACCESS = ((STANDARD_RIGHTS_ALL Or KEY_QUERY_VALUE Or _
    KEY_SET_VALUE Or KEY_CREATE_SUB_KEY Or KEY_ENUMERATE_SUB_KEYS _
    Or KEY_NOTIFY Or KEY_CREATE_LINK) And (Not SYNCHRONIZE))
    
Public Function DefaultMail() As String
    Dim hKey As Long
    Dim sRetVal As String
    Const MAX_PATH = 260&
    If RegOpenKeyEx(HKEY_CLASSES_ROOT, "\mailto\shell\open\command\", _
     0, KEY_ALL_ACCESS, hKey) = ERROR_SUCCESS Then
        sRetVal = String(MAX_PATH + 1, vbNullChar)
        If RegQueryValueEx(hKey, vbNullString, 0&, REG_SZ, _
         ByVal sRetVal, MAX_PATH + 1) = ERROR_SUCCESS Then
            DefaultMail = Left$(sRetVal, InStr(sRetVal, vbNullChar) - 1)
        End If
        Call RegCloseKey(hKey)
    End If
End Function

You have to parse the return value of the DefaultMail function since it will return the path to the mail client including information on how to open it to mail someone... Just run it and you'll see what you need to do.