What is a blacklist?
Is it a list that is black ! he he he, no its not. It is a list that keeps a track of spam activity over the Internet. These are also commonly wellknown as DNSBL and RBL i.e., DNS blacklist and Realtime Blacklist. The sole purpose of this list is to collect the data about spam activities all over the Internet and keep it tracked, so it can be used to reference. The main purpose of this blacklist is to facilitate the legitimacy of the traffic through mail throughout the Internet i.e., avoid spamming or spoofing. The most common ones are listed as follows:
- bl.spamcop.net :: www.spamcop.net/bl.shtml
- cbl.abuseat.org :: cbl.abuseat.org/lookup.cgi
- dnsbl-1.uceprotect.net :: www.uceprotect.net/en/rblcheck.php
- (pbl. sbl. and xbl.)spamhaus.org :: www.spamhaus.org/lookup/
- b.barracudacentral.org :: barracudacentral.org/rbl/removal-request
- Sorbs.net :: www.au.sorbs.net/lookup.shtml
How will you check if you are on their list:
All the blacklist providers will have their own database (collection of IP involved in spamming), so you may have to query your IP individually through their IP lookup tool. However, they are high in numbers, not just one or two of them who you can contact and get it done. Practically, it is impossible to get it done through each and every blacklist provider. To sort things, you can take a reference of mxtoolbox links provided in their blacklist section that will check 100s of blacklist at the same time for you, so you can focus on only those who has listed your IP in their blacklist.
How does it work?
The mail server can be configured to check the incoming mail against the DNS blacklists to distinguish spam vs legitimate mails. In this way, the mail server checks the header of the incoming mail for IP address and then performs a DNS lookup into the DNSBLs to check for the IP listing.
Apart from these DNSBLs, some of the standard mail service provider, like the hotmail for example, has their own list that helps protect their users from spam, phishing, and spoofing.. This is their internal policy rules to classify the incoming mails category.
IP delisting process is something that varies depending upon the list it is on. In the above section, we have discussed something on how to check this.
For Office 365 : https://sender.office.com/