When I am sending an e-mail, by default my font style is Arial. How can I change the font style so that when I am writing a new e-mail the font does not revert back to Arial, which it does at present.
Assuming you are using Outlook as your email client:
Click on Tools>Options
Depending on your version of Outlook, the window will have a Tab like 'Mail Format'. Click this tab and you will have a button called 'Stationary & Fonts' (or similar). If you click that and you can set default fonts for your new mail, replies, forwards, etc.