I want to add a "sign up for newsletter" button on all my client (20) websites. I offer a proprietary newsletter for a vertical market. The client sites don't yet do email capture.

BACKGROUND: All the sites use different technology... some are CMS's, some not, all random. Some sites may be 10 years old - who knows. And I am not the web developer for any of these sites and don't wish to be. I am however, the one who will manage email collection and I will execute monthly email campaigns for each client.

Can you advise on my thinking: to avoid site integration issues, I'm planning to have the sign up tab forward to my server, on which the email collection database would reside. Is this correct? All this needs is a link to me and I get out of hairy site issues. How is this done. Subsequently, I suppose I can export from my database to Constant Contact, Mailchimp or even Excel if necessary. Am I thinking this thru right and what kind of application or preferably off the shelf system should be used, thanx.