A client has provided us with an excel spreadsheet of around 10,000 email addresses, names and addresses. They were taken from a CRM used previously. I've been asked to "clean" up this database - such as check for invalid addresses - (email format, existing mailboxes etc). I've done a bit of Googling and came up with a few "Email List Cleaning Services". Here is one such company. Now my question is - does anyone have any experience with this kind of service, and is it a legitimate service? Alternatively, what are my options for "cleaning" this list? I ask as MailChimp, our preferred email marketing tool, will terminate account access if a certain percentage of emails bounce, (and I imagine similar e-shot services operate on the same basis), to comply with anti-spam regulations etc. This is a legitimate cause, although it may sound quite the contrary.