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InterMail – Port 25 Blocking FAQ
In recent years, many ISPs have begun blocking port 25 in an effort to stop spam from being sent
from their networks. This document answers some of the questions you may have about port 25
blocking (filtering).
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What is port 25 blocking?
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How is ITSSN.com preventing spammers from using their mail servers?
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How can I tell if I am using InterMail?
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Why do I need to use SMTP Auth?
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My ISP is blocking mail and I can’t send mail to InterMail. Can SMTP Auth help me?
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If I use my Webmail interface to check my mail, do I need to change anything?
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What changes do I need to make if I use an
email client (Microsoft Outlook) to check my
mail?
1. What is port 25 blocking?
Port 25 is the default communication channel used for mail sent between a computer and a
mail server. Unfortunately, since there are no restrictions on the use of this port, spammers
can break into other people’s computers and deliver unsolicited bulk
email (spam) via this
port.
Many ISPs (YOUR INTERNET
SERVICE PROVIDER) have found that the easiest way to control this problem is to block port 25. As a
result, any traffic coming from a system that uses port 25 is disregarded.
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2. How is ITSSN.com preventing spammers from using their mail servers to deliver
unsolicited mail?
For our customers on InterMail, we now support the use of secure Simple Mail Transfer
Protocol (SMTP) authentication for outgoing email, which help ensures that our mail servers
as not used by spammers as open relays.
SMTP is the technique used for sending virtually all email on the Internet. SMTP AUTH is a
feature that allows a mail server to allow only authenticated users to send mail. Users are
authenticated if they provide a valid username and password or are within the same network
as the mail server.
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3. How can I tell if I am using InterMail? If you can access your
email via the Web interface at the following URL, you have InterMail:
http://webmail.registeredsite.com.
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4. Why do I need to use SMTP Auth?
We encourage users to configure their email clients for secure SMTP authentication
as soon as possible as this mail server feature is becoming standard for Internet
Service Providers (ISPs). The following are benefits of SMTP Auth:
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SMTP Auth provides better security and a direct connection to our outgoing mail server,
allowing you to bypass your local ISP’s outgoing mail server.
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SMTP Auth adds another layer of security to our mail servers, which should improve
overall services and keep out those who attempt to abuse or spam through our servers.
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SMTP Auth improves connectivity for outgoing mail by allowing the user to make a direct
connection to the InterMail outgoing mail server without having to relay through a local
ISP’s mail server. It also has the benefit of giving mobile users who switch hosts the
ability to use the same mail server without the need to reconfigure their mail client
settings each time.
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5. My ISP is blocking mail and I can’t send mail to InterMail. Can SMTP Auth help me?
Many ISPs have already started blocking traffic on the standard SMTP port (port 25) in order
to protect themselves from blacklisting. These customers can now use our SMTP Auth
servers, which run on port 587, in order to send mail.
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6. If I use my Webmail interface to check my mail, do I need to change anything?
No. If you access your email exclusively through your Webmail interface at
http://webmail.registeredsite.com, you should not have to make any changes. However, if you
are using an email client to access your email, then you may need to make a change.
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7. What changes do I need to make if I use an
email client (Microsoft Outlook) to check
my mail?
InterMail users should configure their
email clients as follows:
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The outgoing SMTP server should be set to
smtp-auth.registeredsite.com
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The outgoing (SMTP) port should be set to
587
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You should select the option for My server requires authentication in Outlook
or similar setting if you use another
email client.
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