DIAGNOSTIC PLAYBOOK
MX points to a CNAME: correct the destination
An MX target should be a hostname with address records rather than a CNAME alias. An alias chain introduces a noncompliant dependency and can behave differently across mail systems.
HealthCheck Email editorial team · · Examples are illustrative
How to investigate
- Query the MX target for CNAME, A and AAAA records to expose its actual structure.
- Ask the receiving provider for the supported canonical mail hostname.
- Update the MX destination and verify both DNS and a controlled incoming message.
What this looks like
ILLUSTRATIVE EXAMPLE
The MX points to an alias originally created for a web application. It resolves in a browser-oriented lookup but is not the intended mail destination.
A mistake to avoid
Do not replace a managed provider target with an arbitrary address you observed once. Its supported hostname allows the provider to manage infrastructure changes.
Keep the result in context
The authoritative DNS service publishes records; recursive resolvers may retain earlier answers until their cache expires. Save the queried name, record type, resolver, answer and time. A website loading correctly does not establish that email records are present or that an SMTP server accepts mail.
Take the next step
Use the related check to gather evidence, then compare it with the affected message or service. Keep the result and time with your notes so a later change can be distinguished from the original problem.
Sources and further reading
The protocol references below explain the underlying behavior. Your sending or DNS provider supplies the account-specific settings for its service.