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Why eMail Verifier loves port 25 so much

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eMail Verifier really requires full access to port 25 in order to work, don't waste your time trying with other "alternative" ports, that doesn't work. eMail Verifier is not an email client, it doesn't connect to your SMTP server. eMail Verifier actually connects to other's mail servers and this type of connection is done exclusively thru the port 25. Why this?

Well, "Port 25" is just 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. Some independent SMTP servers support an additional port other than 25 (26, 587, 2525...) to allow users with authenticated access to connect to them even if port 25 is blocked. Unfortunately eMail Verifier can't use such alternative port as it needs to connect to each address SMTP relay server, not only your server. Relay servers (MTA) only work on port 25. In fact, all e-mail sent via the Internet is routed through port 25. When you run eMail Verifier on your computer, it always uses port 25 to connect to remote e-mail 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.

A few ISPs are blocking port 25. They are doing this to cut down on the amount of spam that is sent from their networks. All e-mail sent via the Internet is routed through the port 25, the channel used for communication between an e-mail client and an e-mail server. Port 25 blocking allows ISPs to block spam sent out through their networks, but it tends to punish the innocent that have a need to use tools like eMail Verifier or to send through e-mail servers other than those belonging to their ISP. The ISPs that block port 25 require their SMTP server to be used instead of the remote SMTP server or a SMTP server running on your computer.

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.

You can easily check whether you are affected by port blocking by using eMail Verifier itself, just verify a single address, an address from anyone but you, I mean, do no use any of your own addresses. Then go to the eMail Verifier console panel and look at the text returned by the server:

- If port 25 is not blocked you will get a successful response with code '220' like this:

eMail Verifier connection log for successful verification

- If port 25 is blocked you will get several connection retries followed by a timeout:

eMail Verifier connection log when port 25 is blocked


Stan Busk - Software Engineer
at www.maxprog.com






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Stan Busk Stan Busk
January 14, 2019



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Stan Busk If you want to make the most of the software that you have acquired at Maxprog, do not miss the Stan's Blog. It is a library of Tutorials and Tips covering specific features and tipical problems you may have when using our tools. This page is updated regularly depending on the topics discussed in our public forums and issues reported thru our HelpDesk. If you are interested on what we are currently working on (or want to participate in beta testings) don't miss the Stan's Logbook.
For years, MAX Programming has provided companies around the globe with sophisticated and innovative solutions. Our commitment to quality is not only evident in our products, but also in our people. It is our mission in Professional Support Services to ensure that our products perform to the fullest of their ability in order to meet the business objectives of our customers. We provide the tools and information required for improved productivity. To accomplish this, we offer an array of services including: Technical Support, Education Services and Consulting Services.

Maxprog is part of an internet site network made of desktoolset.com, emaildesignstudio.com, familycash.com, icash.promo, maxbulkmailer.com, maxprog.com, maxprog.net, maxprog.org, maxprog.us, myrecipients.com, newslettercomposer.com, sharedcontents.com, stanbusk.com, usertools.com.
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).

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