A DNS MX (Mail Exchange) record is a type of resource record in the Domain Name System (DNS) that specifies the mail server responsible for accepting email messages for a particular domain name. It is used by mail transfer agents (MTAs) to route email messages to the correct destination.
When someone sends an email to an email address, the sender’s Mail Transfer Agent queries the Doman Name System to look up the Mail Exchange record for the recipient’s domain. The Mail Exchange record contains the hostname of the mail server that is responsible for accepting incoming email messages for that domain. The sender’s Mail Transfer Agent then connects to the recipient’s mail server and delivers the email message to the appropriate mailbox on that server.
How Mail Exchange records work
Mail Exchange records work by assigning a priority to each mail server that is responsible for accepting email messages for a specific domain. When an email message is sent to a specific domain, the email client or server will perform a Domain Name System look up for the Mail Exchange record(s) associated with that domain. Some domains will have multiple Mail Exchange records with different priorities.
The sender’s Mail Transfer Agent will then try to connect to the mail server with the lowest priority first. If that server is unavailable, it will try the Mail Exchange record with the next highest priority, until it can successfully deliver the email message.
In some cases, a network administrator may set high-priority Mail Exchange records to point to a non-responsive server and then configure their actual mail server to the lowest-priority Mail Exchange record in an effort to deter spammers. The idea here is that a spammer would give up after trying the non-responsive servers in the high-priority Mail Exchange records first.
Why Mail Exchange records are important for email delivery
Mail Exchange records are essential for email deliverability, because they allow email clients and servers to know where to deliver email messages for a particular domain.
The use of Mail Exchange records for a domain is considered standard practice, and without valid Mail Exchange records it is unlikely that email messages will be delivered to their intended recipients. By correctly configuring Mail Exchange records, email messages are more likely to be delivered to the correct mail server and will have a better chance of being delivered successfully to the recipient’s inbox.
Why Mail Exchange records are not a guarantee for email delivery
While Mail Exchange records are an important part of email deliverability, they are not the only factor that affects whether email messages are delivered successfully. Other factors that can affect email deliverability include:
- Spam filters: Email messages that are flagged as spam by spam filters may not be delivered to the recipient’s inbox, even if the Mail Exchange records are correctly configured.
- IP reputation: If the IP address associated with the mail server has a poor reputation, email messages may be flagged as spam or rejected by recipient email servers.
- Authentication: If the email messages are not authenticated using the SPF, DKIM, or DMARC protocols, they may be flagged as spam or rejected by recipient email servers.
- Email content: If the email messages contain suspicious or malicious content, they may be flagged as spam or rejected by recipient email servers.
- Incorrect Domain Name System settings: If the Mail Exchange records are not set up correctly in the Doman Name System settings, email messages may not be delivered to their intended recipients.
- Firewall restrictions: Some firewalls may block incoming email messages from mail servers that do not have a valid Mail Exchange record.
- Spoofing: Attackers may spoof Mail Exchange records to redirect email messages to their own servers, allowing them to intercept and read sensitive information.
- Malware: Malware on a mail server can modify the Mail Exchange records to redirect email messages to a different server.
Why you need an Email Validation service
Mail Exchange records are a critical component of email deliverability, and their correct configuration is essential for ensuring that email messages are delivered successfully. However, they are not a guarantee for email deliverability on their own, and other factors such as spam filters, IP reputation, authentication, and email content can also affect email deliverability.
Not all organizations will use Mail Exchange records, even though using them is considered standard practice. Mail Exchange records may also be misconfigured, sometimes intentionally. That is why it is important to use an email validation system that understands how Mail Exchange records work and how they are just a component of how email messages are delivered. Using a service like DOTS Email Validation – 3 can help organizations ensure that their email messages are delivered to the intended recipients and avoid potential issues with email deliverability.
