The problem you are having is due to Port 25 blocking. This blocks any 3rd party outgoing mail servers from being accessed while connected to your ISP network via Dialup, DSL or Cable. Many ISP's (Internet Service Providers) are blocking what is called "Port 25" which is the port used to send e-mail. They have chosen to do this to cut down on the amount of "SPAM" mail that is sent. All e-mail sent via the Internet is routed through the port 25, the channel used for communication between a mail client and a mail server. 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. The 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. Here are some web sites that can help you find thousands of ISPs:
You can check with your dial-up provider to see if they are doing this. Here are a few of the major ISP's that block Port 25:
AT&T (can be unblocked at the request)
Comcast (Offer a Business Class account with full access to port 25
Verizon (can be unblocked at the request)
You can check whether you are affected by port blocking using Telnet.
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