Interestingly enough while perusing my usual youtube subscriptions and recommendations I came accross a video that claims that you can do this with a free service called Zapier.com. Zapier is a new online software that allows you to splice together different web tools so that they act as one. For example let's say you add and event to your Google Calender with Zapier you could set up an action so that automatically a Tweet would also be sent at the same time. What makes this site so interesting is that PayPal is one of the services that you can hook up to an e-mail service like MailChimp or Aweber. This is all explained in the following video:
According to the comments left many people believe that this does in fact comply with eBay's TOS. I am not too sure on whether it does or does not. I'm guessing that all is okay since your are only sending an invitation to join a mailing list and they still must double opt-in to receive e-mails. The problem arises when and if one of your customers decides to complain about your mailing to eBay. It would probably be a good idea to use an e-mail that is not associated with any of your eBay accounts to do the mailing.
Jim Cockrum is also the author of the highly successful book The Silent Sales Machine which is now in its Seventh Edition.