Why do i need one

local applications make a call to the default e-mail application to send mail. While there is nothing wrong with your current mail these applications can't access web mail (Gmail, yahoo mail, hotmail). Iinstalling a local mail client like Thunderbird, and setting it up to link to your current mail will allow these local applications to work and send through these web mail services.
 

ittimjones

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if you click on a link anywhere in the OS or on the web that says Mailto: (email address) the default email client (Outlook or Thunderbird) installed on the computer will open and open a new email with that email address in the To Field and the From field filled in w/ your default email account that you have set up in that client. if you have not set up an account in a client, than u will get this message. if you ONLY use webmail, you will get this message
 

ittimjones

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be on alert though, your mailbox might be broken. you may want to go outside and check it and ensure that nothing on it is broken. The mailman might have updated his system that your mailbox wasn't working correctly. might wana talk to him about the error you got on your computer.