How to Send Email from Localhost without Exposing Credentials?

Sending Email using Java

Error:

The error "javax.mail.MessagingException: Could not connect to SMTP host: localhost, port: 25; nested exception is:java.net.ConnectException: Connection refused: connect" occurs when trying to send an email from a localhost without a properly configured mail server.

Solution:

The provided code will work to send email using Google's SMTP server. However, in this solution, you will need to enter your Google username and password to authorize the sending process, which may raise security concerns.

Alternative Solution using GoogleMail API:

For a more secure method, it is recommended to use GoogleMail API with OAuth2 authorization. The updated code snippets provided in the answer section demonstrate how to construct an authorized Gmail service and send emails using the API.

Step-by-Step Guide:

1. Enable the Gmail API in your Google Developer Console.
2. Obtain credentials by running the authorize() method.
3. Construct a MimeMessage object containing the email details.
4. Convert the MimeMessage to a Gmail Message object.
5. Send the email using the Send() method of the GoogleMail class.

Benefits of using GoogleMail API:

• Improved security: OAuth2 authorization ensures that you are not storing your Google account credentials in your code.
• Modern approach: GoogleMail API provides a modern and efficient way to send emails.
• Additional functionality: The API offers features such as email tracking and labeling.

Additional Notes:

• Load Email Address: The loadEmail() method in the Utils class can be used to retrieve the previously authorized email address.
• Save Email Address: The saveEmail() method in the Utils class can be used to save the authorized email address.
• Logout: To logout of a Gmail account, delete the StoredCredential and email files in the getGmailDataDirectory() directory.

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