How to Find User's Email Address

• Download source - 5.4 KB
• Download GetDefaultEmailAddresses - 72 KB

Introduction

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.

Background

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 users 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:

HKEY_CURRENT_USER\Software\Microsoft\IdentityCRL

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()
{
    HKEY key;
    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;

    TCHAR  achValue[MAX_VALUE_NAME];
    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.

        if (cSubKeys)
        {
            wprintf(TEXT("\nNumber of email accounts used: %d\n"), cSubKeys);

            for (i = 0; i < cSubKeys; i++)
            {
                cbName = MAX_KEY_LENGTH;
                retCode = RegEnumKeyEx(key, i,
                    achKey,
                    &cbName,
                    NULL,
                    NULL,
                    NULL,
                    &ftLastWriteTime);
                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.

There, you will find all the installed MAPI clients.

You can also determine the default one by looking at:

HKEY_LOCAL_MACHINE\SOFTWARE\Clients\Mail\Default.