You can send an email using Thunderbird. It is quite straightforward as you do not need to log in to the cPanel webmail manually. You can send an email directly using the Thunderbird email client.
1. Open Thunderbird.
2. On the left side of the top menu, click on New Message.
If you have multiple email accounts, click on your account, and a drop-down menu will open. Then select the appropriate email and enter the email account of the person you want to send an email to in the To field.
In the subject field, enter the subject of your email, enter your message in the Message box, and then click on Send.
Hope you found this article useful.