Port 25 blocking fully prevents email validation to be possible actually!
eMail Verifier requires full access to port 25 in order to work. eMail Verifier needs to connect to each address relay server. Relay servers only work on port 25.
Port 25 is a network connection channel. Some Internet Service Providers (ISP) intercept port 25 so it is not possible to use eMail Verifier nor any software using port 25.
When you run eMail Verifier on your computer, it always uses port 25 to connect to remote email relay servers. Therefore, if your ISP is blocking the port, eMail Verifier will be unable to fully test e-mail addresses, 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.
Unfortunately, there is nothing we can do to change this. Port 25 is the standard for sending messages and the one eMail Verifier uses. The only solutions are either to contact your ISP and see if they can remove that block or switch to another ISP. Smaller local ISP's usually do not block Port 25.
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).