Email Verifier - Validate that an email address is valid using Java, ColdFusion, or PHP. The tool checks address syntax, dns mx records, and the mail server without sending an email. - http://www.activsoftware.com/email/verify/
Mail Validator - verifies email addresses are deliverable in a email list. - http://www.mailvalidator.com
Bulk Email Verify Express - Fast Professional Bulk Email Address and Mailing List Verify Management Software. - http://www.email-tool.com/verify.html
Fast Email Verifier - Checks a validity of e-mail addresses in databases, address books , spreadsheets or any other mailing lists. Nothing is sent to the recipient. - http://www.lencom.com/verifier.html
FreshAddress.com - Email List Building, Correction and Updating - Our e-mail appending, e-mail list cleaning and correction, and ECOA (e-mail change of address and updating) services help you build and update your e-mail list. - http://www.freshaddress.com/biz