How to use it
- Enter a domain, or paste an email address (only the part after @ is used).
- Read the MX records in priority order: lower numbers are tried first, and equal numbers share the load.
- Check the detected provider and each server’s IPs; red notes are mistakes that will affect incoming mail.
- Carry on to build SPF, check blacklists or run the full SPF/DKIM/DMARC check.
What an MX record does
An MX (Mail Exchanger) record tells every mail server on the internet where to deliver mail for you@example.com. Each record has a priority number and a server host name; senders try the lowest number first and move on if it fails.
MX only controls where incoming mail goes. Whether your outgoing mail is trusted depends on SPF, DKIM and DMARC, and the mail server IP’s reverse DNS (PTR) and blacklist status also affect delivery.
Common MX mistakes
Old MX records left behind after changing provider: some mail goes to the old server, so messages arrive only sometimes.
MX pointing at a CNAME or a bare IP address: RFC 2181 and RFC 5321 forbid it and some senders refuse to deliver. Create an A record first and point the MX at that host name.
Wrong host field: most DNS providers (Aliyun, DNSPod, Cloudflare) use “@” for the root domain; entering www or mail puts the MX on a subdomain.
Only one MX: fine when the provider has its own redundancy; a self-hosted setup should add a backup MX with a higher number.
MX records of common mailbox providers
Always use the values shown in your provider’s console; this table is for cross-checking, and a single typo stops mail arriving.
| Provider | MX | Note |
|---|---|---|
| Google Workspace | 1 smtp.google.com | Domains set up since 2023 need only this record; the older five ASPMX.L.GOOGLE.COM records still work. |
| Microsoft 365 / Outlook | 0 example-com.mail.protection.outlook.com | The host name is built from your domain (dots become hyphens); use the one shown in the Microsoft 365 admin center. |
| Tencent Exmail / QQ Mail | 5 mxbiz1.qq.com / 10 mxbiz2.qq.com | The two standard Tencent Exmail records. |
| Alibaba Mail (Aliyun) | 5 mxn.mxhichina.com / 10 mxw.mxhichina.com | The two standard Alibaba Mail records. |
| NetEase Mail (163) | 10 qiye163mx01.mxmail.netease.com / 50 qiye163mx02.mxmail.netease.com | A common NetEase business mail setup; check the NetEase console. |
| Zoho Mail | 10 mx.zoho.com / 20 mx2.zoho.com / 50 mx3.zoho.com | Zoho US data centre; EU, India and China data centres use their own domains. |
Frequently asked questions
How long do MX changes take to apply?
It depends on the old record’s TTL, typically minutes to a few hours. This tool asks public DNS, which may still cache the old value; check again after the TTL has passed.
Which priority numbers should I use?
Use the values your provider gives you. The numbers only set the order, so 1 and 10 behave like 10 and 20; servers with the same number share the load.
The MX looks right but mail still does not arrive. What next?
Read the bounce code the sender received and look it up in the SMTP bounce code tool; then check whether the mailbox is full, active and not blocked by a spam gateway, and whether the sending IP is blacklisted.
Can it test whether the mail server accepts connections (SMTP test)?
Not yet. This tool only queries DNS and never connects to port 25; an SMTP connection test will come as a separate tool.