You need to state more clearly what you require - is Blueyonder your ISP or some other company?
If it's the latter, you need to make it the Default acccount from Tools>Accounts>highlight your ISP>Set as Default. Any other accounts will retain their normal POP3 and SMTP configuration but Send and Receive (from the Connections tab) through your ISP or LAN (Use this Account).
You can follow the basic configuration for OE from the majority of ISPs' Help pages, such as:
When I open to send a new message the text is always "Arial" size 10, I'd like to set it "Times New Roman, size 12 permanently, I've tried to do it via Tools > format, however whenever I open a new message, it just keeps reverting back to "Arial" size 10.