What does a 'no MX' bounce reason mean and what are the possible causes?
Summary
What email marketers say11Marketer opinions
Email marketer from SparkPost details that 'no MX' bounces typically indicate a problem with the recipient's domain DNS settings. It suggests the sender verify the domain's MX record using online tools before resending.
Email marketer from DNSQueries explains that a missing MX record leads to email delivery failures and outlines that this can happen from simple DNS errors, a typo or incorrect record value. If the issue persists, the DNS might not have propagated. Also advises to use their DNS checker to check the record is set up correctly.
Marketer from Email Geeks explains that `no mx` likely means the receiving domain doesn’t have an MX record, which is how mail is routed. They further suggest it could indicate people are providing made-up domains.
Email marketer from Email Geeks explains that as per RFC, domains can still accept mail with just an A record, mostly for legacy reasons. He mentions it's still common in Southeast Asia, but if not active in that area, a domain without an MX record often means no email server is set up. He ends by suggesting to ask your ESP for clarification.
Email marketer from Mailjet explains that a 'no MX' error could mean the domain is newly registered and records haven't propagated, or the domain owner hasn't set up email hosting. Another possibility is that the MX record was recently changed, and the DNS cache hasn't updated yet.
Email marketer from Reddit explains that a missing MX record means that there is no information on how emails should be delivered to that domain. This means any messages sent will bounce back.
Email marketer from StackOverflow explains that 'no MX' errors can be caused by typos in the recipient's email address. Check the email address is valid and then check the domain's MX record using online tools or command-line utilities like `dig` or `nslookup`.
Email marketer from EmailDeliveryBlog explains that a missing MX record indicates that the domain is not set up to receive email. This is often due to incorrect configuration of DNS settings or a failure to properly register the domain for email services.
Email marketer from EasyDMARC explains that MX record misconfiguration is often due to incorrect hostname specification or syntax errors. They recommend careful syntax checking and proper hostname formatting within the DNS settings.
Email marketer from WebHostingTalk explains that to fix a missing MX record, you need to log into your domain's DNS management panel and add the correct MX record(s) provided by your email hosting provider. Ensure the correct priority and hostname are used.
Email marketer from Email Geeks explains that "unable to connect to MX servers" could mean the receiving server was too busy, causing the sending server to give up. He expects this to be uncommon with major providers, so it may still be caused by list quality issues.
What the experts say2Expert opinions
Expert from Email Geeks points out that domains without an MX record can still accept mail and suggests asking the ESP what they mean when they suppress mail with that error. He also suggests both messages are coming from the ESP, and the wording isn't ideal, advising to ask them to clarify. He adds that they probably mean those addresses are iffy/typoed/bad, but you can't be sure.
Expert from Word to the Wise explains that a missing MX record means no server is configured to receive mail for that domain. Common causes include recent domain registration where DNS records haven't been properly configured or propagated, or the domain owner simply doesn't want to receive email at that domain. Additionally, incorrect DNS settings or temporary DNS server issues could be the cause.
What the documentation says4Technical articles
Documentation from DNSimple explains that an MX record specifies a mail server responsible for accepting email messages on behalf of a recipient's domain, and a preference value is defined, which determines the order in which mail servers should be tried.
Documentation from RFC 5321 describes that MX records are used to locate the mail exchangers for a domain. If no MX records are found, the address is treated as if it has no mail forwarding capability.
Documentation from Google Workspace Admin Help explains that MX records are essential for directing email to the correct mail server. A 'no MX record' error indicates the domain lacks this record, preventing email delivery.
Documentation from Cloudflare states that if a user doesn't configure their MX record at all for the domain, any email sent to their domain will bounce and the sender will most likely get a 'no MX record found' message.