It looks as if you've set up your business email account with the SMTP server adress of your work server. The trick is to have the proper adress in the 'incoming server' box (ie. 'post.bigbusiness.com') and have your ISP's SMTP server in the 'outgoing server' box (ie. 'smtp.wanadoo.co.uk') for your business mail account. If you still get the same error message, then your ISP is not redirecting mail for some reason. Worth a try though.