(Unicode C) OAuth2 for a GMail using a P12 Service Account Key

See more GMail REST API Examples

Note: This example does not work for Personal Google Accounts where the email domain is @gmail.com

For more information, see https://www.chilkatsoft.com/google_workspace_setup_smtp_gmail.asp

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#include <C_CkHttpW.h>
#include <C_CkCertW.h>
#include <C_CkMailManW.h>
#include <C_CkEmailW.h>

void ChilkatSample(void)
    {
    HCkHttpW http;
    HCkCertW cert;
    BOOL success;
    const wchar_t *iss;
    const wchar_t *scope;
    const wchar_t *oauth_sub;
    int numSec;
    const wchar_t *accessToken;
    HCkMailManW mailman;
    HCkEmailW email;

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    http = CkHttpW_Create();

    // --------------------------------------------------------------------------------
    // For a step-by-step guide for setting up your Google Workspace service account,
    // see Setup Google Workspace Account for Sending SMTP GMail from a Service Account
    // --------------------------------------------------------------------------------
    // Begin by loading your Google service account key (.p12)
    cert = CkCertW_Create();
    success = CkCertW_LoadPfxFile(cert,L"c:/someDirectory/keys/chilkat25-cbd7b42afbd8.p12",L"notasecret");
    if (success != TRUE) {
        wprintf(L"%s\n",CkCertW_lastErrorText(cert));
        CkHttpW_Dispose(http);
        CkCertW_Dispose(cert);
        return;
    }

    // The ISS is your service account email address ending in gserviceaccount.com.
    iss = L"chilkatsvc@chilkat25.iam.gserviceaccount.com";

    // The scope is always the following string:
    scope = L"https://mail.google.com/";

    // The sub is your company email address
    oauth_sub = L"bob@yourcompany.com";

    // The access token is valid for this number of seconds.
    numSec = 3600;

    accessToken = CkHttpW_g_SvcOauthAccessToken(http,iss,scope,oauth_sub,numSec,cert);
    if (CkHttpW_getLastMethodSuccess(http) != TRUE) {
        wprintf(L"%s\n",CkHttpW_lastErrorText(http));
        CkHttpW_Dispose(http);
        CkCertW_Dispose(cert);
        return;
    }
    else {
        wprintf(L"access token: %s\n",accessToken);
    }

    // The access token allows us to send unlimited emails while it's valid. Once it expires, we must obtain and use a new one.

    // -----------------------------------------------------------------------
    mailman = CkMailManW_Create();

    // Set the properties for the GMail SMTP server:
    CkMailManW_putSmtpHost(mailman,L"smtp.gmail.com");
    CkMailManW_putSmtpPort(mailman,587);
    CkMailManW_putStartTLS(mailman,TRUE);

    CkMailManW_putSmtpUsername(mailman,L"bob@yourcompany.com");
    CkMailManW_putOAuth2AccessToken(mailman,accessToken);

    // Create a new email object
    email = CkEmailW_Create();

    CkEmailW_putSubject(email,L"This is a test");
    CkEmailW_putBody(email,L"This is a test");
    CkEmailW_putFrom(email,L"Bob <bob@yourcompany.com>");
    success = CkEmailW_AddTo(email,L"Recipient",L"recipient@example.com");
    // To add more recipients, call AddTo, AddCC, or AddBcc once per recipient.

    success = CkMailManW_SendEmail(mailman,email);
    if (success != TRUE) {
        wprintf(L"%s\n",CkMailManW_lastErrorText(mailman));
        CkHttpW_Dispose(http);
        CkCertW_Dispose(cert);
        CkMailManW_Dispose(mailman);
        CkEmailW_Dispose(email);
        return;
    }

    success = CkMailManW_CloseSmtpConnection(mailman);
    if (success != TRUE) {
        wprintf(L"Connection to SMTP server not closed cleanly.\n");
    }

    wprintf(L"Successfully sent email using Gmail with a service account key.\n");


    CkHttpW_Dispose(http);
    CkCertW_Dispose(cert);
    CkMailManW_Dispose(mailman);
    CkEmailW_Dispose(email);

    }