The last three things i have sold in the Market place when i went to send an invoice it came back as returned mail. These were three different people. With obviously different e-mail addresses.

Any ideas?

This is unfortunately caused by your email provider, Yahoo, blocking email you create and send through the marketplace. This is a common problem but unfortunately out of our hands. The only option we can offer is for all members to use someone other than Yahoo, or AOL who block emails in much the same way. Gmail works very well as do Hotmail.

BTW, I have moved your thread to the Marketplace Support forum.