Basic SMTP reply code · RFC 5321

530 Authentication required

The server requires authentication for this command and the client has not authenticated (RFC 4954). Some servers also use it when STARTTLS must come first.

Class: 5yz · Permanent failure
5yz: a permanent failure. The same request should not be repeated; something must change first, such as the address (RFC 5321 §4.2.1).
Associated enhanced codes
The enhanced codes that usually come with this code, per the registry and the providers:

5.5.15.7.0
Source
RFC 4954

How 530 appears at providers

The exact text from the provider's documentation, as you see it in the bounce, and what it means.

Gmail

530 5.7.0Authentication required.

The server requires authentication before sending.
530 5.7.0Must issue a STARTTLS command first.

The client must start TLS (STARTTLS) before this command (RFC 3207).

Have the whole error message?

Sources: RFC 5321 · RFC 3463 · RFC 3464 · IANA · Gmail · Microsoft 365 · read on 26 September 2026