We recommend that you follow the guidelines for permission-based mailing and do not send to any contact that you have not mailed to in the last two years. This article provides helpful information.
You might want to read this case study about email data hygiene from Marketing Sherpa.
Zift Solutions Channel Engagement Team may be able to help or you may want to contact a reputable email marketing company such as iContact, Constant Contact or MailChimp.