I have just opened a new thunderbird account but do not want to send e-mails in that name. Can I change it or set up a new account?

So, you want to use the account you just set up with the email address you indicated, but you want the messages you send to have a different "friendly" name than what you originally used, right? That can be changed to anything you like at any time. Go to <Account Settings | (the account in question) | Default Identity | Your Name> - change that to whatever you want. This is your default Identity and by default all new messages will show that name. You can also set up multiple identities that can have various other friendly names, and you can choose from them when you create a message. Here's an article that goes into detail about that feature: https://support.mozilla.org/en-US/kb/using-identities You can also edit the "From" name on the fly when you're in the message creation window by choosing "Custom From Address" from the From drop-down list.