Setting up the correct Thunderbird SMTP settings for Gmail is essential if you want to send emails smoothly from your Gmail account through Mozilla Thunderbird. Gmail requires secure authentication, proper ports, and correct encryption protocols. If any of these are wrong, you may face errors like “Outgoing server not working,” “Authentication failed,” or “Unable to send message.” This detailed guide explains the full configuration process along with troubleshooting tips.

Why Email SMTP Settings Are Important for Thunderbird?

SMTP is responsible for sending emails from Thunderbird to Gmail’s servers. Gmail uses strong security standards like OAuth2, SSL/TLS, and two-factor authentication. Using incorrect SMTP settings may prevent Thunderbird from sending messages or cause repeated login errors.

Step 1: Enable IMAP & SMTP in Email Settings

Before configuring Thunderbird, ensure Gmail allows email programs to connect.

• Go to Email on your browser.
• Open Settings → See All Settings.
• Select the Forwarding and POP/IMAP tab.
• Enable IMAP.
• Ensure SMTP Access is allowed in your Google account security.

Step 2: Use These Email SMTP Settings in Thunderbird

Open Thunderbird and go to Account Settings → Outgoing Server (SMTP) and add or edit Gmail SMTP details:

• Server Name: smtp.gmail.com
• Port: 587
• Connection Security: STARTTLS
• Authentication Method: OAuth2 (recommended)
• User Name: Your full Gmail address

If STARTTLS fails, you may use:

• Port: 465
• Connection Security: SSL/TLS

Step 3: Allow Thunderbird Access to Your Google Account

When Thunderbird connects for the first time, a Google sign-in window appears. Login using your Gmail ID and allow Thunderbird to access emails, contacts, and sending permissions. If you do not grant permissions, outgoing emails will fail.

Step 4: If You Use 2-Step Verification (2FA)

If your Google account has two-factor authentication enabled, Gmail may block old password-based login. In this case, either use OAuth2 or generate an App Password.

Step 5: Fix Email SMTP Not Working in Thunderbird

If sending fails, try the following fixes:

• Update Thunderbird to the latest version.
• Make sure Allow less secure apps is OFF (Gmail no longer supports it).
• Enable OAuth2 instead of Normal Password.
• Check if your antivirus or firewall is blocking outgoing SMTP ports.
• Clear saved passwords from Thunderbird and reconnect Gmail.
• Re-login to your Google account from the Authentication window.

Step 6: Test Your Gmail SMTP Connection

Send a test email from Thunderbird. If successful, your Gmail SMTP settings are correctly configured. If not, verify:

• Correct port (587 or 465)
• Correct encryption (STARTTLS or SSL/TLS)
• Valid Gmail login credentials
• OAuth2 authorization success