Why Did Apple Devices Show Certificate Errors on March 20, 2020?
In March 2020, Apple devices displayed security warnings because the HTTPS certificate for appleimap.163.com had expired due to NetEase Mail’s failure to renew it, highlighting how overlooked certificate management can disrupt services and underscoring the need for automated monitoring tools in large organizations.
On the evening of March 20, 2020, many Apple users on iOS, iPadOS, and macOS saw repeated pop‑up warnings that the system could not verify the server identity of “appleimap.163.com”.
The warning indicated that the HTTPS certificate for that domain was untrusted because the certificate had expired.
The cause was a simple oversight: NetEase Mail failed to replace the wildcard digital certificate before its expiration at 8 p.m. on March 20, 2020.
Normally service providers renew certificates before they expire to ensure the operating system trusts them, but NetEase’s lapse triggered Apple’s security alert, suggesting a possible spoofed server.
In reality, no man‑in‑the‑middle attack occurred; the issue was solely the expired certificate.
This incident shows that NetEase likely lacks automated tools for monitoring or auto‑renewing certificates, leading to the failure.
After user reports, NetEase promptly replaced the server certificate, and users can restore normal mail operation by re‑configuring their NetEase mail accounts.
Such basic mistakes—forgetting to renew certificates—are common in large companies with complex product lines; Microsoft Teams suffered a similar outage when its certificate expired.
Both cases highlight the need for automated certificate‑checking tools that issue reminders before expiration.
Below are some user comments on the incident:
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