Access denied due to DNSBL

Why would you get a message like this "Denied access due to DNSBL listing." when trying to access a mail service?

Occurrence
It happens when I am using Digicel internet to access Telecom Vanuatu (TVL) webmail.

Equipment
EGDGE/GPRS USB Modem

Digicel internet is sourced from Fiji.

IP Address: 202.170.40.71

Carrier APN Settings
Source: http://modmyi.com/wiki/index.php/Carrier_APN_Settings


DIGICEL FIJI
Connection Settings(GPRS/EDGE)
Data Account Name WEB: Digicel
GPRS Access Point Name (APN): web.digicelpacific.com
PPP Authentication Type: Default
GPRS Username / Data Account: N/A
GPRS Password / Data Account: N/A
Private or Public?: Public
Primary DNS Server IP: Na
Secondary DNS Server IP: Na

Wap Settings Settings name – Digicel Wap
Session Mode – Permanent
Connection Security – Off
Data Bearer – GPRS
GPRS access point – wap.digicelpacific.com
IP address – 10.150.122.12
Authentication Type – Normal
Proxy Port – 8081
MMS Settings Settings Name – Digicel MMS
Homepage – .http://mms.digicelpacific.com:8990
Session Mode – Permanent
Data Bearer – GPRS
GPRS access point – wap.digicelpacific.com
IP address – 10.150.122.12
Authentication Type – Normal
Port - 808

Telecom Vanuatu Webmail
http://webmail.vanuatu.com.vu

What is a DNSBL?
Source: http://www.dnsbl.info/

Domain Name System Blacklists, also known as DNSBL's or DNS Blacklists, are spam blocking lists that allow a website administrator to block messages from specific systems that have a history of sending spam. As their name implies, the lists are based on the Internet's Domain Name System, which converts complicated, numerical IP address such as 140.239.191.10 into domain names like example.net, making the lists much easier to read, use, and search. If the maintainer of a DNS Blacklist has in the past received spam of any kind from a specific domain name, that server would be "blacklisted" and all messages sent from it would be either flagged or rejected from all sites that use that specific list.DNS Blacklists have a rather long history in web terms, with the first one being created in 1997. Called the RBL, its purpose was to block spam email and to educate Internet service providers and other websites about spam and its related problems. Although modern DNS Blacklists are rarely used as educational tools, their function as an email blocker and filter still serves as their primary purpose to this day. In fact, almost all of today's email servers support at least one DNSBL in order to reduce the amount of junk mail clients using their service receive. The three basic components that make up a DNS Blacklist - a domain name to host it under, a server to host that domain, and a list of addresses to publish to the list - also haven't changed from the time when the RBL was first created to today.Since then, dozens of different DNSBL's have sprung up and are available for use, and they all have their own lists that are populated based on what does or doesn't meet their own standards and criteria for what a spammer is. Because of this, DNS Blacklists can vary greatly from one to the other. Some are stricter than others, some only list sites for a set amount of time from the date the last piece of spam was received by the maintainer versus others that are manually maintained, and still others not only block IP addresses, but also entire ISP's known to harbor spammers. This results in some lists working better than others because they are maintained by services with a greater level of trustworthiness and credibility than competing lists might have. Users can also use these differences to decide on which DNS Blacklist works best for them depending on what their specific security needs are. Less lenient lists might allow more spam to get through, but might not block non-spam messages that have been misidentified on lists that have stricter guidelines for what goes on or what is left off of it. To help facilitate this, DNS Blacklists that are intended for use by the public will usually have a specific, published policy detailing what a listing means and must adhere to the criteria laid out in it in order to not only attain public confidence in their services, but to sustain it as well.Webmail services or Internet Service Providers use certain DNSBL service on their network.Some of these DNSL have blacklisted 202.170.40.71.In order to solve the problem, the IP address needs to removed from the block list.

Tested 202.170.40.71 with DNSBL.info Quick DNSBL Check

Results:81
Total 8 Listed

Conclusion

Webmail services or mail poviders use certain DNSBL service to reduce junk and spam mails.

TVL mail DNSBL provider have listed 202.170.40.71 and the IP address needs to be removed from the black list in order for webmail to be accessible.

The IP is Fiji Fintel's and it is listed in some DNSBL databases (www.dnsbl.info).

I posted a note on AVONSYS website with this questions, "how can it be corrected and who is responsible?".

Here's Franck Martin's response:

Contact FINTEL, it is their problem and contact telecom-vu webmail, they should not use DNSBL to block access to websites. All DNSBL lists are saying this is just plain wrong to do that!

So I need to know why TVL is using DNSBL in webmail, so i send a short note to my ISP and here's a response from my ISP.

The DNSBL is the process to identify IP that sending SPAM and black list those IP which is blocking some service as webmail.

We do not control that process but you can ask the person concern to clean up is PC (Scan for anti virus) and it will be release automatically from the black list controlled by SPAMHAUS.

The IP i got was assigned by Digicel Vanuatu and it is not a fixed IP.