5.7.0 Must Issue a Starttls Command First Thunderbird Email

Method 1: Checking the SMTP settings

On your computer, launch the Mozilla Thunderbird email client first.
Next, give a right-click on your email account available at the left-side panel.
Select the Settings option from the pop-up menu.
This will open the Account Settings window on your Thunderbird email client.
Select your email account from the displayed list and click the Server Settings button to check the server settings.
Navigate to the left-side panel and click the Outgoing Server (SMTP) tab.
In the Outgoing Server (SMTP) window, you can modify the SMTP settings for your account.
Select your account from the displayed list and click the Edit button to access the SMTP Server window.
Make sure that the STARTTLS option is selected in the Connection security drop-down menu.
Verify whether you have entered the appropriate port number for the selected encryption type.
Check whether you have entered the correct email address in the Server Name field.
Click OK and try sending a test email. Check if the error 5.7.0 must issue a starttls command first thunderbird has been resolved.

On your Windows computer, open the Control Panel app and click on Programs and Features.

Select the Uninstall a program option and choose the Thunderbird program from the displayed list.

Click the Uninstall/Change button and confirm your action.

After uninstalling the Thunderbird app, reinstall it.

Add your email account again in the Thunderbird email client and check if the problem has been resolved.

If the 5.7.0 must issue a starttls command first thunderbird problem persists, contact our technical support team.