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 invalid addresses 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.
We are pleased to offer you two software products designed to check e-mail addresses for existence — Advanced Maillist Verify (AMV), which does the two-phase checking (DNS and SMTP) and detect all possible dead emails, and High Speed Verifier (HSV), which only performs the first phase (DNS).
AMV is helpful when you need to thoroughly check relatively small mailing lists (containing no more than 50..100 thousand addresses). Advanced Maillist Verify is also capable of checking addresses in databases, address books of popular applications, it has COM/ActiveX Interfaces for integration into various software systems and CGI/ISAPI modules for simpler integration into wed-servers. However, technical principles underlying AMV interface solutions don't allow using it for longer lists.
High Speed Verifier is offered as a solution for quick removal of garbage from lists with millions of addresses. For purely technical reasons, its operating rate is 10..15 times greater than that of AMV with relatively small lists, and with lists containing millions of addresses the difference in operating rate might be up to thousands of times. Growth of the HSV operating rate with longer lists is ensured by the fact that HSV stores the results of all queries to DNS servers in RAM cache, so, with longer lists the rate of cache hits is greater.
