An MX (mail exchanger) record tells sending mail servers which hostnames can receive email for a domain. When a sender delivers a message, it looks up MX records for the recipient address’s domain, then uses their preference values to order eligible destinations: the lower number is preferred.
What an MX record does
MX stands for mail exchanger. The record associates a mail domain with a named host willing to receive or handle mail for it. For an address such as [email protected], the sender looks up MX records for example.com. This lets a domain route incoming mail to designated servers rather than requiring the domain name itself to accept SMTP connections. See RFC 1035 and RFC 5321.
As an Amazon Associate I earn from qualifying purchases.
An MX record contains a preference number and an exchange hostname. It points to a hostname, not directly to an IP address. After selecting an exchanger, the sender must resolve that hostname to an address; choosing an MX record and resolving its host are separate steps.
How MX priority works
Lower numerical preference means higher delivery preference. RFC 5321 puts it plainly: “Lower numbers are more preferred than higher ones.” The number controls ordering; it does not describe a server’s speed, quality, or capacity.
#1 Best Overall
- Dual band router upgrades to 1200 Mbps high speed internet (300mbps for 2.4GHz plus 900Mbps for 5GHz), reducing buffering and ideal for 4K stream
- Full Gigabit Ports - Gigabit Router with 4 Gigabit LAN ports, ideal for any internet plan and allow you to directly connect your wired devices
- Boosted Coverage - Four external antennas equipped with Beamforming technology extend and concentrate the Wi-Fi signals
- MU-MIMO technology - (5GHz band) allows high speeds for multiple devices simultaneously
- Access Point Mode - Supports AP Mode to transform your wired connection into wireless network, an ideal wireless router for home
| Preference | Exchange | Meaning |
|---|---|---|
| 10 | mx-primary.example. |
Preferred before the entry with preference 20 |
| 20 | mx-secondary.example. |
Less preferred; an alternate destination |
In this example, a sender normally attempts the preference-10 exchanger first. The preference-20 host gives it an alternative to try, but the record alone does not guarantee that every sender will switch immediately or behave identically during an outage.
What happens when preferences match
If multiple MX records have the same preference, RFC 5321 says a sender should randomize among them when there is no clear reason to favor one. This can distribute delivery attempts among equivalent exchangers, but it does not promise perfectly even traffic or load.
Rank #2
- 【Five Gigabit Ports】1 Gigabit WAN Port plus 2 Gigabit WAN/LAN Ports plus 2 Gigabit LAN Port. Up to 3 WAN ports optimize bandwidth usage through one device.
- 【One USB WAN Port】Mobile broadband via 4G/3G modem is supported for WAN backup by connecting to the USB port. For complete list of compatible 4G/3G modems, please visit TP-Link website.
- 【Abundant Security Features】Advanced firewall policies, DoS defense, IP/MAC/URL filtering, speed test and more security functions protect your network and data.
- 【Highly Secure VPN】Supports up to 20× LAN-to-LAN IPsec, 16× OpenVPN, 16× L2TP, and 16× PPTP VPN connections.
- Security - SPI Firewall, VPN Pass through, FTP/H.323/PPTP/SIP/IPsec ALG, DoS Defence, Ping of Death and Local Management. Standards and Protocols IEEE 802.3, 802.3u, 802.3ab, IEEE 802.3x, IEEE 802.1q
Why a backup MX may not take over as expected
Several factors affect alternate delivery. SMTP senders can limit the number of alternate addresses they try and control their retry behavior; RFC 5321 says they must be capable of trying relevant alternatives and should try at least two addresses. The exact timing and behavior therefore depend on the sending system as well as the published records.
- The preferred exchanger may still be reachable but rejecting or deferring delivery, rather than being unavailable.
- The sender may be using cached DNS data, so it may not yet see a recent change.
- The sender’s alternate-address limit or retry schedule may affect when another host is attempted.
- An alternate exchanger may not be configured to accept mail for the domain even if its hostname resolves.
How to check or change MX records
- Get the exact values from your mail provider. Use its current setup instructions for the MX hostnames and preference numbers. The standards define how values are interpreted, not which values a particular provider requires.
- Check the authoritative DNS zone. Confirm that the intended MX records are published there and look for stale or conflicting entries before editing.
- Check each exchange hostname. Confirm that it resolves to usable addresses and that the receiving mail service is configured to accept mail for your domain.
- Allow for caching. DNS resolvers and sending systems may retain answers according to the configured TTL, so a change is not necessarily visible to every sender immediately.
If mail is not reaching an expected backup, check whether the intended records are visible in authoritative DNS, whether the sender has current DNS data, whether the preferred host is actually unavailable or rejecting delivery, and what retry and alternate-host limits the sender uses.
Rank #3
- Dual-band Wi-Fi with 5 GHz speeds up to 867 Mbps and 2.4 GHz speeds up to 300 Mbps, delivering 1200 Mbps of total bandwidth¹. Dual-band routers do not support 6 GHz. Performance varies by conditions, distance to devices, and obstacles such as walls.
- Covers up to 1,000 sq. ft. with four external antennas for stable wireless connections and optimal coverage.
- Supports IGMP Proxy/Snooping, Bridge and Tag VLAN to optimize IPTV streaming
- Access Point Mode - Supports AP Mode to transform your wired connection into wireless network, an ideal wireless router for home
- Advanced Security with WPA3 - The latest Wi-Fi security protocol, WPA3, brings new capabilities to improve cybersecurity in personal networks
What MX records do not configure
MX records handle incoming-mail routing. They do not, by themselves, prove that mail is configured correctly end to end, set up outbound authentication, or guarantee inbox placement. SPF, DKIM, and DMARC serve different purposes; changing MX records does not configure them.
Quick Recap
Best Value
- Next-Gen Gigabit Wi-Fi 6 Speeds: 2402 Mbps on 5 GHz and 574 Mbps on 2.4 GHz bands ensure smoother streaming and faster downloads; support VPN server and VPN client¹
- A More Responsive Experience: Enjoy smooth gaming, video streaming, and live feeds simultaneously. OFDMA makes your Wi-Fi stronger by allowing multiple clients to share one band at the same time, cutting latency and jitter.²
- Expanded Wi-Fi Coverage: 4 high-gain external antennas and Beamforming technology combine to extend strong, reliable, Wi-Fi throughout your home.
- Improved Battery Life: Target Wake Time helps your devices to communicate efficiently while consuming less power.
- Improved Cooling Design: No heat ups, no throttles. A larger heat sink and redefined case design cools the WiFi 6 system and enables your network to stay at top speeds in more versatile environments.
Rank #4
- DUAL-BAND WIFI 6 ROUTER: Wi-Fi 6(802.11ax) technology achieves faster speeds, greater capacity and reduced network congestion compared to the previous gen. All WiFi routers require a separate modem. Dual-Band WiFi routers do not support the 6 GHz band.
- AX1800: Enjoy smoother and more stable streaming, gaming, downloading with 1.8 Gbps total bandwidth (up to 1200 Mbps on 5 GHz and up to 574 Mbps on 2.4 GHz). Performance varies by conditions, distance to devices, and obstacles such as walls.
- CONNECT MORE DEVICES: Wi-Fi 6 technology communicates more data to more devices simultaneously using revolutionary OFDMA technology
- EXTENSIVE COVERAGE: Achieve the strong, reliable WiFi coverage with Archer AX1800 as it focuses signal strength to your devices far away using Beamforming technology, 4 high-gain antennas and an advanced front-end module (FEM) chipset
- OUR CYBERSECURITY COMMITMENT: TP-Link is a signatory of the U.S. Cybersecurity and Infrastructure Security Agency’s (CISA) Secure-by-Design pledge. This device is designed, built, and maintained, with advanced security as a core requirement.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
