You can use Outlook Express to receive your email from all your email accounts. It has an audible signal to notify you whenever an email message arrives.
Hope this helps.
In OE you can have your email accounts created under different 'identities'. So you would create a separate identity for your trading email account, and set OE to 'Play sound sound when new message arrives' for that identity. To check you other email accounts you can simply switch between identities while you're in OE.
I'm sure there are other email clients or utilities programs which can do the same thing. If that's what you want let me know and I'll look it up for you.
To add a new account in OE:
Run OE, then from the Tools menu select Accounts.., click on the Mail tab, click the Add.. button, select Mail. This will start the Internet Connection Wizard for each email account you want to create. Follow the instructions which are basically straight forward, except for the server name and type which depends on which email provider you are setting up (e.g. yahoo, hotmail, gmail etc). Here are the instructions for hotmail account: (by the way ms keeps trying to make it difficult for people with free hotmail account to receive their mail in this manner. Gmail is a far better choice in this and many other regards.)
When the wizard opens the Email Server Name dialog box, select HTTP in the 'My incoming mail server is a" field, then select Hotmail in the 'My email service provider' field.
Now that you have the email account set up, you need to tell OE how to receive the mail. From the Tools menu, select Options.., in the General tab, make sure the boxes 'Play sound when new messages arrive' and 'Check for new messages every" are checked, and select the time interval for OE to check your mail.
I hope that will do it for you. Let me know if you need further help.