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What are DNS MX record, DNS A-record, rDNS and how does it work?

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    Email is one of the most important aspects of digital marketing, so understanding the technology behind it is essential. 

    DNS MX record, DNS A-record, rDNS are all part of making sure your emails get delivered properly to customers and prospects – but do you know how they work?

    In this blog post we’ll look at what each term means and why it matters for email marketers. We’ll also explore how domain name servers (DNS) works with sending emails from a webmail platform like Gmail or Outlook giving you complete control over mail flow in every possible way! 

    Get ready to take a dive into the world of brilliant technical jargon and awesome bots who manage our data interchange.

    What is MX record?

    A DNS MX record is a type of DNS record that stores the mail exchange server for a domain. It is used to redirect emails to the right place.

    Every domain name you own has an MX record associated with it. If you have multiple domains, they all have their own MX records.

    MX records contain two pieces of information:

    🔹 The hostname of your mail server

    🔹 Priority number assigned to each mail exchange server

    Why do I need to configure DNS MX Records?

    MX stands for Mail eXchanger and is an important part of the email experience. This is a record that a domain owner sets up to tell other servers where they can send emails for that domain. An MX record is usually associated with an A record, which indicates where the server hosting your domain can be found.

    When you set up an MX record, you tell other mail servers which server(s) you want them to use when trying to send email for your domain. The DNS server checks this entry before sending the message so it knows where to send it if it can’t connect directly.

    This is useful because it helps prevent spam from your domain and allows you to manage the delivery of messages from multiple domains without having to manage each one individually.

    MX records for your email providers

    If you use third-party services such as Google Apps or Office 365, they will most likely provide you with two MX records: one for sending mail and one for receiving. The receiving MX must point to their servers, while the sending MX must point to your own server.

    If you don’t have third-party services, you may only need one MX record pointing to your own server.

    MX preferences and priorities

    When you send an email, your computer contacts the mail server and asks it to deliver the message. The mail server has all the information about where to send the message. It looks at the destination address (the To: field) and finds the best server to deliver it to.

    But if you have multiple mail servers for your domain, how does your computer know which one to use?

    It uses the order of precedence. Mail servers with a higher priority access servers with a lower priority. If there are two servers with the same priority, the server with the lowest numerical value is bound first.

    The order of precedence is determined by your DNS records (MX records). The lower number has the higher priority. Thus, if you have multiple mail servers configured with different priorities, they will be contacted in order from lowest number to highest.

    How are MX records queried in DNS?

    DNS queries are a fundamental part of how the Internet works. When you enter a URL in a browser, your computer makes a request for this website’s IP address to your Internet Service Provider’s (ISP) DNS server.

    MX records are one type of DNS record used to look up the location of an email server. Like any other type of DNS records, MX records are queried through DNS servers. The difference is that instead of looking up domain names like “google.com”, you’re looking for their associated mail server addresses.

    When an email is sent to the recipient’s mail server, the receiving MTA queries the sender’s DNS to check the mail exchange servers responsible for sending the email. This is done by looking up information published in the sender’s DNS MX records.

    How to look up and verify your DNS MX records?

    If you are a domain owner, it’s a good idea to keep a close eye on your DNS records to keep your domain healthy and your email up and running. This requires frequent DNS lookups and checks should be an integral part of your work cycle at regular intervals.

    What is A-Record?

    The A-record is one of the key resource records of the Internet. It is needed to link the domain to the IP address of the server. Until the A-record is registered, your site will not work. When you enter the name of the site in the address

    What is a DNS A-record?

    Your hostname is associated with an IP address using an A-record. Record initials mean address or A. One of the most commonly used records in DNS zones, this record is critical to setting up your DNS. The IP address (IPv4) for the provided host is specified in the A-record.

    In other words, it uses the IP address to resolve (or direct) the domain name to the right place. Many things can be accomplished with A-records, including using multiple A-records for the same domain as fallbacks and fallbacks. Each name will have its own A-record pointing to the same IP address if multiple names point to the same address.

    A-records are the most basic DNS records and are often used in DNS servers. A-records can be used for a variety of purposes, including creating multiple A-records for the same domain for redundancy and backup. Multiple names can refer to the same IP address, in which case each of them will have its own A-record referring to the same IP address.

    Why is the A-record needed?

    The A-record is the most basic type of DNS record and is used to point your domain name to a specific IP address. The A-record sets up your site’s home base so that when users type in your domain name, they are taken directly to your site.

    The A-record is a one-to-one mapping of the hostname and IP address. For example, if you have a website hosted at www.example.com, you could create an A-record with the hostname www and IP address (where is the public IP address of your web server).

    When someone visits www.example.com in their browser, their computer queries your DNS server for that hostname on UDP port 53 (DNS) and receives a response containing the IP address The browser connects directly to on TCP port 80 (HTTP) or 443 (HTTPS) to request the content of your site.

    You can have multiple A-records for the same domain name. For example, if you want to install multiple web servers on different IP addresses (to add redundancy), you can create an A-record for each server’s IP address. You can also create multiple mail servers with multiple A-records.

    How to query a DNS entry?

    DNS lookup is the process of obtaining the IP address of a domain name by querying a DNS server.

    Name-based resolution is one method for performing DNS lookups. It involves using a domain name instead of an IP address in the request.

    A typical request has two parts:

    🔹 A hostname, or FQDN (Fully Qualified Domain Name), is used to identify a particular resource. The hostname can be either an official Internet name or an alias that points to a specific device on your network.

    🔹 The request type determines how much information you want to receive in response to your request. This may include:

    The A-record (address record) returns the IP address associated with the given hostname; if there is no A-record, it returns an NXDOMAIN error.

    A-record vs CNAME

    A-records are the default option when you enter a domain name into your hosting account. They are associated with individual IP addresses, which you can find on the DNS (Domain Name System) records page. These IP addresses can be used for email, web services and FTP.

    CNAME records create an alias or “nickname” for a domain name. For example, if you have a site hosted at www.example.com, you can use this entry to create an alias using the name example.com instead of the full address. You can also use CNAME to point multiple domains to the same IP address or to point subdomains to different IP addresses than their parent domains.

    The difference between A-record and CNAME records is that A-records are used to map a domain name to an IP address, while CNAME records are used to map multiple domain names to a single IP address.

    A-record means “address” and CNAME means “canonical name”. So, if you want to host a site at example.com, you’ll need an A-record that maps the domain name to your server’s IP address.

    What is rDNS?

    Reverse DNS lookup or reverse DNS resolution (rDNS) is the determination of a domain name that is associated with a given IP address

    Reverse DNS lookup (rDNS) – reverse DNS lookup – a special domain zone that is designed to determine the name of a host by its IPv4 address using a PTR record.

    What is rDNS for? First of all, it is simply necessary to set up sending corporate mail from your own server. If the server’s IP address does not have an entry in rDNS, then all mail servers will refuse to accept messages from you at the beginning of the session. As a result, you will get errors related to this problem, for example, 550 Your IP has no PTR Record.

    550 is the standard code of the SMTP mail server, which reports a critical error in the mail session. The text that follows the error number explains to the administrator in more detail the reason for the error.

    Setting up rDNS for an IP address is mostly handled by the hosting provider that owns the corresponding block of IP addresses. Therefore, to configure a reverse DNS query, contact technical support.

    It is important to remember that the name of the IP address of the mail server, and especially the corporate mail server, should be given carefully. A good name for a mail server can be a name like: mail.domain.ua, mxt.domain.ua, mx.domain.ua and others. For example, the name host-27.990-454.domain.ua will not be suitable and convenient. And most likely such a name will fall under the spam filter of the client.

    Using a reverse DNS lookup greatly reduces spam, as messages from non-rDNS IP addresses are simply rejected by the mail server. In fact, this is the most effective and least expensive way to protect users from spam. So you should configure reverse DNS lookup to send your mail so that mailers do not consider it as spam.

    Depending on the type of mail server, the presence of rDNS is checked in different ways, for example: 

    🔹 Postfix mailer: you need to enable the function – reject_unknown_client 

    🔹 in Exim server: verify = reverse_host_lookup

    🔹 in the MS Exchange Server: in Exchange Server, go to Servers, select Protocols, then the SMTP protocol, select the SMTP server and select from the Properties list by clicking. Delivery tab → Perform reverse DNS lookup on incoming messages.

    What is reverse DNS used for? rDNS is one of the basic requirements of some network protocols. Among other things, it is a kind of spam filter for checking the IP address from which the message was sent, and checks whether it matches the domain name, if there is no such match, the letter is not delivered.

    Who can manage rDNS? This is done by the owners of IP addresses, including hosting providers that provide services for you.


    These are the four most important DNS records that you need to know about when setting up your website. DNS MX record, DNS A-record, rDNS – each one plays a vital role in ensuring that your website is accessible and visible to everyone who wants to visit it.

    If you’re not sure which DNS records you need or how to set them up, our team of experts can help.

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