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Consulta de Registros MX

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Checks whether all worldwide resolvers return this exact mail server or priority.

Base de Conocimiento · Diagnóstico de Correo

Frequently Asked Questions About MX Records & Email Deliverability

Root causes, technical diagnostics, and enterprise remediation guides in the Anayil Knowledge Base.

What does MX priority or preference mean, and how does it work?

MX priority is an integer that specifies the delivery order sending Mail Transfer Agents (MTAs) must follow when routing messages to your domain. Lower numbers represent higher priority.

🔍 Why does this happen?

SMTP RFC 5321 dictates that servers must first attempt delivery to the host with the lowest numeric value (e.g. 10 before 20). If multiple servers share the same priority, load is distributed via round-robin.

🛠️ How to fix it?

Assign the lowest priority (e.g. 10) to your primary mail server and higher numbers (e.g. 20, 30) to secondary or backup relays. Never invert priorities.

Read full guide in Knowledge Base

Why do emails bounce (550 / 450 errors) after updating MX records?

When MX records change, Internet resolvers do not see the update immediately due to TTL caching on previously queried records.

🔍 Why does this happen?

Intermediate resolvers cache DNS responses until the TTL expires. Senders querying cached resolvers continue delivering to the old server, causing bounces if accounts are closed there.

🛠️ How to fix it?

Lower the TTL to 300 seconds 24 hours prior to migration. Keep accounts active on both servers for 72 hours and use this MX Checker to monitor global synchronization.

Read full guide in Knowledge Base

Why must an MX record NEVER point to an IP address or CNAME?

RFC 2181 (§10.3) and RFC 5321 (§5.1) mandate that an MX record target must be a fully qualified domain name (FQDN) that resolves directly to an A or AAAA record.

🔍 Why does this happen?

Pointing an MX to an IP address breaks SMTP syntax parsers. Pointing it to a CNAME creates resolution loops and latency, leading strict providers like Google or Microsoft to reject mail.

🛠️ How to fix it?

Create an A record for your mail subdomain (e.g. `mail.example.com` pointing to the IP) and set your MX record to point to `mail.example.com`.

Read full guide in Knowledge Base

Are MX records enough to prevent outgoing emails from being flagged as SPAM?

No. MX records only handle inbound mail routing. Outbound deliverability and anti-spam protection require SPF, DKIM, and DMARC authentication.

🔍 Why does this happen?

Modern mail filters require cryptographic and sender identity proof. Unsigned emails or unauthorized IPs will be marked as spam or rejected as phishing.

🛠️ How to fix it?

Configure your SPF TXT record, add the DKIM public key provided by your email host, and enforce a DMARC policy (p=quarantine or reject).

Read full guide in Knowledge Base

How do you migrate between email providers (e.g. Google Workspace to M365) with zero data loss?

Zero-loss migration requires a controlled coexistence window to absorb messages while global DNS propagation completes.

🔍 Why does this happen?

During the 24-48 hour propagation period, incoming messages may land on either the old or new provider depending on sender resolver caches.

🛠️ How to fix it?

Provision mailboxes on the new host first. Update MX records. Keep both systems monitored for 48 hours and perform a final IMAP delta sync before shutting down the old service.

Read full guide in Knowledge Base
Explore all Email guides in the Knowledge Base