Error #103 means eMail Verifier was unable to resolve the address that was specified. A prime example of this would be a mistyped IP address, or a domain name of an unknown or unreachable host.
Note that if you get a lot of errors of that kind it may be because port 25 is blocked by your Internet provider. As a result eMail Verifier can check the syntax of the e-mail addresses and whether the domain they belong to exists but the last step, connecting to the address MX Exchanger, can't be performed. You can try to contact your ISP and see if they can remove that block. You will find more information on this here:
Maintain clean mailing lists checking the validity of recipient's e-mails addresses. eMail Verifier can save time and money for businesses who send newsletters to their clients, nonprofit organizations who send bulletins to their members, or any person or business that needs to maintain a clean e-mail contact list.
eMail Verifier is your powerful solution for the standard "message delivery error." Email Verifier verifies every e-mail address from a given mailing list, allowing you to determine 80-90% of "dead" email addresses.
eMail Verifier works on the same algorithm as ISP mail systems do. Addresses for e-mail are extracted from a Domain Naming Server (DNS) and eMail Verifier tries to connect with SMTP-servers and simulates the sending of a message.
It does not send the message though - eMail Verifier disconnects as soon as the mail server informs the program whether the address exists or not. Email Verifier is a very effective piece of software that can verify over 10 e-mails per second .
It can verify single e-mails or huge lists. (eMail Verifier is multithreaded, providing high speed verifying).