Why Does a Domain’s Email Work Internally but Fail for External Senders?

Internal delivery may use local routing while external senders rely on public MX records and external mail filtering. The two paths can behave differently.

What to check

Check public MX answers, nameserver authority, mail gateway status, accepted domains, external SMTP responses, and recent DNS changes.

Recommended next step

Test from an external mailbox and correct the public routing or filtering issue at its source. Informatix Systems can troubleshoot domains and business email.