The Craving Mind

  Understanding DMARC record DMARC, (Domain-based   Message Authentication Reporting, & Conformance) an open source standard, uses a concept called alignment to tie the result of two other open source standards, SPF (a published list of servers that are authorized to send email on behalf of a domain) and DKIM (a tamper-evident domain seal associated with a piece of email), to the content of an email. DMARC alignment By themselves, SPF and DKIM can associate a piece of email with a domain. DMARC attempts to tie the results of SPF and DKIM to the content of email, specifically to the domain found in the From: header of an email. The domain found in the From: header of a piece of email is the entity that ties together all DMARC processing. Because anyone can buy a domain and put SPF and DKIM into place (including criminals), the results of processing SPF and DKIM have to be related to the domain found in the From: header to be relevant to DMAR...

  A "valid" PTR record is one which resolves to a name which resolves back to the address. For this reason, your PTR records shouldn't use names that resolve back to multiple addresses. Reasoning behind all this (read on only if you care):   There's no rule in the RFC's saying that there must be a PTR record for every A record, though it is listed as a design goal. It also never says that you can't have multiple PTR records for a given address; unfortunately, doing so creates havoc. The reason for this is the way that records are reported and recognized. Suppose you have multiple PTR records for a given address. Then this happens:   1) A request is made for PTR records for the address, by something trying to verify one of the hostnames.   2) The server treats the set of PTR records in round-robin, "load sharing" the results. In effect, it reorders the records in an essentially random permutation, and reports them all.   3) The requester sees a stack ...

Prerequisites 1. A Ubuntu machine (18.04.4 LTS) 2. IP Address 192.168.1.210 3. Hostname  (ns1.example.com) sudo apt update Install DNS Server The package name for the DNS server on Ubuntu is  bind9  and is available in the base repository. Use the  apt  command to install the  bind9  package. sudo apt install -y bind9 bind9utils bind9-doc dnsutils Configure DNS Server The  /etc/bind/  directory is the main configuration directory of the DNS server, and it holds configuration files and zone lookup files. Global configuration file is  /etc/bind/named.conf . You should not use this file for your local DNS zone rather you can use  /etc/bind/named.conf.local  file. Create Zones Let us begin by creating a forward zone for your domain. sudo nano /etc/bind/named.conf.local Forward Zone The following is the forward zone entry for the  example.com  domain in the  named.conf.l...