If you would like to remove email from Mozilla thunderbird, you can simply do it but if you use IMAP, the email will only be removed from your thunderbird email client and the email will be keep on your mail server.
If you apply POP settings, then email will be removed from your Thunderbird Email Client and Main email server also.
1. Open Mozilla Thunderbird.
2. Open Inbox and right click on the email you wopuld like to delete and then just click on the “Delete Message” option.