• AVG DNS Blacklisting

Dear server administrator,

You have contacted us as your email server or a 3rd party's email server is currently black-listed from sending email to Powernet.

What is a blacklist? How does it work?

A blacklist is merely a published list of IP addresses, where the criteria for listing are determined by the publisher. For example, the criteria might be "has been seen sending spam recently".

When someone tries to send mail into one of Powernet's mail servers, we check to see if their IP address is listed by any of our preferred blacklists (see below). If the sending IP address is listed, we refuse mail from that IP address.

Why does Powernet use blacklists?

The vast majority of spam comes from compromised servers or PCs, whereas most legitimate mail comes from a small number of servers which have static IP addresses.

The blacklists list the IP addresses of computers which are known to spam sources, or are known to exploitable by spammers due to security flaws, or are using dynamic IP addresses.

By employing blacklists, we help to fight spam worldwide while providing protection and improved levels of service to our customers.

The blacklists on our servers correctly identify and block many thousands of spam emails every day. This benefits us and our customers in two major ways:

1. Legitimate email is delivered more quickly.
2. Our customers receive less spam in their mailboxes.

Where do these blacklists come from?

The blacklists used by Powernet are maintained by non-profit organisations dedicated to the reduction of spam mail:

• Spamhaus (http://www.spamhaus.org/)

  • Spamhaus maintains two blacklists, both of which are used by Powernet:
  • sbl.spamhaus.org - Known spammer IP addresses
  • xbl.spamhaus.org - IP addresses of servers vulnerable to exploit by spammers

• SORBS (http://www.dnsbl.sorbs.net/)

  • SORBS maintains several blacklists, with different listing criteria. Powernet uses the following the SORBS lists:
  • dul.dnsbl.sorbs.net - Dynamic IP ranges
  • http.dnsbl.sorbs.net - Open HTTP Proxy Servers
  • socks.dnsbl.sorbs.net - Open SOCKS Proxy Servers
  • misc.dnsbl.sorbs.net - Other (not HTTP or SOCKS) Proxy Servers
  • smtp.dnsbl.sorbs.net - SMTP servers open to relaying
  • web.dnsbl.sorbs.net - List of web (WWW) server which have spammer-abused vulnerabilities
  • block.dnsbl.sorbs.net - List of hosts demanding they are never tested by SORBS
  • zombie.dnsbl.sorbs.net - List of networks hijacked from their original owners, some of which are already used for spamming

Both of the blacklist suppliers above are used by numerous other ISPs worldwide.

How do I get my mail server removed from the blacklists?

In order to check the status of your blacklist entry and/or remove yourself, please follow these instructions:

Spamhaus

1. Visit: http://www.spamhaus.org/

2. Click on the "Check IP" link below "SBL Advisory". Check your server's IP address.
3. If your server is listed on the SBL (Spammers Block List), follow the the instructions on the site for removal.
4. If your server is listed on the XBL (Exploits Block List), fix your system so that it is no longer vulnerable before following the instructions on the site for removal.
5. Await confirmation of removal by Spamhaus.

SORBS

If you are listed on the "dynamic IP address" list (dul.dnsbl.sorbs.net) list:

• If the SORBS listing is accurate (i.e. your IP address is, indeed, dynamic):
  • Get a static IP address instead
  • Or, send your mail out via another server which has a static IP address - for example, your ISP's mail server.
• Alternatively, if the SORBS listing is inaccurate (i.e. your IP address is static)
  • Contact SORBS (or get your ISP to contact SORBS) to get their listing fixed.
  • Or, send your mail out via another server which has a static IP address - for example, your ISP's mail server.

If you are listed on one of the other SORBS lists:

1. Visit: http://www.dnsbl.sorbs.net/ and firstly check the IP address of your email server to determine if you are black-listed.

2. Check your email server is not vulnerable, open to exploitation by spammers or otherwise flawed.

3. Once you've fixed any vulnerabilities on your mail server, visit http://www.dnsbl.sorbs.net/retestFAQ.html and follow the instructions to re-test your server for removal from the list.

4. Await confirmation of removal by SORBS.

Please DO NOT ask Powernet to remove your IP address from any of these blacklists. We have no control over them. You must contact the blacklist owner, as described above.

However, if you have any other queries about sending mail to Powernet or Powernet customers, please contact our support team at support@powernet.co.uk.

Yours sincerely,

The Powernet support Team <support@powernet.co.uk>