Following a question in Stack Overflow, I wrote this article which is about finding the user's email address, or several email addresses if he/she has.
I looked at the Registry to find out how to do so, by searching for my own email address at the entire Registry. This is rather a tricky method to find out (in all probability) the user's email address from the stored email used to log on to Microsoft services. There are many email clients and methods, among them web mail (Gmail, Yahoo, etc.) and desktop clients (Outlook) and yet, assuming the typical user will use the main email address to sign in to Windows (and most of the Windows user use their Windows account's credentials to even log in to their PC), this works!
Using the code
Windows stores used email accounts used as "Live ID" in the "UserExtendedProperties" key in
The assumption is that this email was selected by the user as the Windows user name to log in to the PC and/or to other WIndows services.
Therefore you can get the email accounts using the following code:
// void GetDefaultEmailAddress()
TCHAR achKey[MAX_KEY_LENGTH]; // buffer for subkey name
DWORD cbName; // size of name string
TCHAR achClass[MAX_PATH] = TEXT(""); // buffer for class name
DWORD cchClassName = MAX_PATH; // size of class string
DWORD cSubKeys = 0; // number of subkeys
DWORD cbMaxSubKey; // longest subkey size
DWORD cchMaxClass; // longest class string
DWORD cValues; // number of values for key
DWORD cchMaxValue; // longest value name
DWORD cbMaxValueData; // longest value data
DWORD cbSecurityDescriptor; // size of security descriptor
FILETIME ftLastWriteTime; // last write time
DWORD i, retCode;
DWORD cchValue = MAX_VALUE_NAME;
if (RegOpenKeyEx(HKEY_CURRENT_USER, L"Software\\Microsoft\\IdentityCRL\\UserExtendedProperties", NULL, KEY_READ, &key) == ERROR_SUCCESS)
// Get the class name and the value count.
retCode = RegQueryInfoKey(
key, // key handle
achClass, // buffer for class name
&cchClassName, // size of class string
NULL, // reserved
&cSubKeys, // number of subkeys
&cbMaxSubKey, // longest subkey size
&cchMaxClass, // longest class string
&cValues, // number of values for this key
&cchMaxValue, // longest value name
&cbMaxValueData, // longest value data
&cbSecurityDescriptor, // security descriptor
&ftLastWriteTime); // last write time
// Enumerate the email accounts subkeys, until RegEnumKeyEx fails.
wprintf(TEXT("\nNumber of email accounts used: %d\n"), cSubKeys);
for (i = 0; i < cSubKeys; i++)
cbName = MAX_KEY_LENGTH;
retCode = RegEnumKeyEx(key, i,
if (retCode == ERROR_SUCCESS)
wprintf(TEXT("(%d) %s\n"), i + 1, achKey);
Points of Interest
When it comes to desktop applications used for email (i.e. MAPI clients) the place to look in order to enumerate these clients, is the
Software\Clients\Mail Key in HKEY_LOCAL_MACHINE.
You will find there all installed MAPI clients
You can also determine the default one by looking at: