Power Email Verifier   
http://tecsoftware.biz

Power Email Verifier can check your email lists for valid emails. It can import large lists with no problem. Uses multithreading to verify emails at a very fast rate. Simulates the sending of email without sending any messages. Program supports the following file formats: delimited, text, csv - windows address book, and over 7 mail list formats. Verified email records are saved in the same format that they are imported in. Program comes completely pre-configured, just load list and go!

BulkVerifier   
http://www.rafasoft.com

Welcome to BulkVerifier, an efficient multi-threaded application for checking e-mail addresses and domain availability. Quickly and easily verifies email addresses, huge domains and clean up your mailing / domain list. A powerful advanced bulk domain and email validation tool. BulkVerifier offers you two processing modes fast and deep. In its fast mode BulkVerifier works extremely fast being able to process mailing lists containing dozens of millions of e-mail addresses at a speed of several thousands addresses per second. This mode does not ensure the highest accuracy of checking/cleaning but is optimal by expended time and traffic and provides quite sufficient results. We recommend the fast processing mode of BulkVerifier as a high-speed tool for sifting obvious rubbish out of large mailing lists containing millions of e-mail addresses. In its deep mode (default), BulkVerifier works significantly slower but provides much more precise results. Optimal data amount for this mode is 70...100 thousand e-mail addresses. We recommend the deep processing mode of BulkVerifier as a slow but high-quality tool for checking of not very large mailing lists. BulkVerifier can process both plain list of e-mail addresses / domains where each line contains one item and files of more complex structure like CSV file where lines represents multi-field records of the same structure (i. e. containing the same fields separated with the same delimiter). For example, you can export a worksheet of an MS Excel file to check availability of e-mail addresses/domains listed there. It’s supposed that one line of an incoming file contains one e-mail address and/or one domain.

EmailVerifier   
http://www.email-business.com

Keep your email lists up to date and remove email addresses which do not exist any longer. You just have to define the path of your email lists. As a result you receive a list with guaranteed valid email addresses, a list containg probably valid email addresses and a list with invalid email addresses. The EmailVerifier uses a proper proofing mechanism, because most of the mail servers have disabled the standard checking command. Further it exposes mail servers, which give the OK return value for every email address.

Advanced Email Verifier   
http://www.glocksoft.com

Advanced Email Verifier (AEV) is your powerful solution for the "message delivery error". AEV is designed for system administrators, webmasters, programmers as well as for those advanced users who have their own mailing lists and need to keep them up-to-date. When Internet users move from one service provider to another, some of them do not take their email addresses with them. Users who lost their email accounts may not notify you of their loss. Internet users may choose to subscribe to your service with a phony email address so that they have access to a free download or a free offer that you may be providing online. Hence, you are left with dead email addresses. There is no need to disturb your clients and friends anymore to check if their email addresses are still valid. AEV connects directly to the SMTP servers and checks the emails for you. Nothing is sent to the recipient. AEV verifies every email address from a mailing list or database and determines up to 70-80% of "dead" email addresses. Other 20-30% of emails cannot be verified by any email verifying program. This happens because the appropriate mail servers receive all the messages regardless of whether the email address is valid or not, and then return the message if the email address doesn't exist anymore. AEV supports the import of email addresses from Paradox, DBase, Excel, Text (.CSV), HTML, Word, Lotus 1-2-3, QuattroPro, XML, MS Access files, and DBISAM tables (.dat files). You can also connect to the database on your disk and verify the email addresses directly from the database. AEV helps you maintain your mailing list clean and decrease the Internet traffic keeping you from sending undeliverable messages that cause a ping-pong of useless messages between SMTP servers.

High Speed Verifier   
http://www.mailutilities.com

High Speed Verifier (HSV) is a high-speed software designed to check e-mail address for existence. HSV is capable of checking thousands of addresses per second. It can easily deal with mailing lists containing tens millions of addresses; moreover, it is with this list size that the program's highest performance can be achieved. HSV detects about 20-30% of invalid addresses in a mailing list, though theoretically it is possible to detect up to 60-70% using a software product. This figure seems relatively small, but actually it might make 10% of a list. Besides, HSV provides for optimal checking mode in terms of time and data traffic. More thorough checking (with which the rest 40% of dead emails could be detected) takes 10 times longer and requires 5 times greater traffic for each address, hence it's not that advisable with huge lists.