Got it, let's break down how to set up unique, secure keys for each of your apps to send emails via Gmail without hardcoding your main account credentials. Here are the two most reliable approaches, depending on your setup:

This is the simplest option if you're using a personal Gmail account with two-factor authentication (2FA) enabled:

• First, make sure your Gmail account has two-factor authentication (2FA) turned on — this is a mandatory requirement for using App Passwords.
• Log into your Google Account, navigate to the "Security" settings page.
• Under the "Signing in to Google" section, locate the "App Passwords" option.
• Click "Create", then give this password a descriptive name tied to your specific app (like "Blog Notification Service" or "Order Alert Tool").
• Google will generate a 16-character random password — copy this string, and use it as the dedicated "App Key" for that app.
• Create a separate App Password for every application you manage. If you ever need to revoke access or update credentials for one app, you only need to delete/re-generate that specific password without affecting others.

For better control and enhanced security (especially for production apps), OAuth 2.0 is the ideal choice. It lets you create unique credentials for each app without sharing your main account password:

• Log into the Google Cloud Console, create a new project (or use an existing one).
• Enable the Gmail API for your project (search for it in the API Library and toggle it on).
• Go to "APIs & Services" → "Credentials", then click "Create Credentials" → "OAuth client ID".
• Set up the OAuth consent screen (internal apps for your own use don't need public verification; external apps will require Google's review process).
• Select the app type (e.g., "Desktop app", "Web app") that matches your use case, and create a separate OAuth client ID + secret for every application.
• Each app will use its own client ID and secret to request access tokens, which are used to authenticate with the Gmail API to send emails.
• Pro tip: Restrict each app to only the permissions it needs (like the https://www.googleapis.com/auth/gmail.send scope, which only allows sending emails — no access to read your inbox).

最佳实践 #

• Never hardcode these keys into your project files! Use environment variables (like a .env file) or a secrets management tool (e.g., AWS Secrets Manager, HashiCorp Vault) to store them securely.
• Rotate your keys periodically, especially if you suspect an app's credentials might have been compromised.
• For OAuth 2.0, always follow the principle of least privilege — only grant the minimal permissions each app needs to function.

内容的提问来源于stack exchange，提问作者user576510