480 Authentication Required

The exchange that produces this is short and worth picturing. The server sends its greeting, the client sends a command such as GROUP or MODE READER, and the server replies 480 because it has not been told who is asking. A correctly configured client answers with AUTHINFO USER, then AUTHINFO PASS, and continues. A session log containing a single 480 followed by successful transfers is a healthy session, not a fault.

A prompt, not a rejection

Nothing has been refused at the point 480 is sent. The server has made no judgement about whether the credentials are good, because it has not received any. This is the whole distinction from 481, which is a verdict delivered after credentials were supplied. It also separates 480 from 502, where the server has decided the session may not proceed at all. Treating 480 as a password failure sends a reader off changing a password that was never tested, which is the single most common wasted step on this error.

Where the credentials actually go missing

When 480 persists rather than appearing once, the cause is nearly always local configuration:

• The username and password fields in the server entry are empty. Settings imports, container rebuilds, and configuration files copied between machines commonly drop the password while keeping the hostname and port.
• An email address was entered where the provider issues a separate username, or the two fields were transposed.
• The client has an explicit toggle for whether the server requires a login, and it is off. Some newsreaders will not send AUTHINFO at all until that box is ticked, so they loop on 480 forever with perfectly valid credentials sitting in the fields.
• The account is IP authenticated and the connection is arriving from an address that is not on file, so the server falls back to asking for a login the reader may never have been issued.
• Trailing whitespace pasted into either field, which is invisible in most settings dialogs.

Assigning fault and confirming the fix

Fault sits on the local machine in the great majority of cases. The server behaved to specification; it asked, and nothing answered. The exception is a provider that has changed its authentication requirements, which is rare and would be visible as every client on every machine failing at once rather than one client on one machine. A useful confirmation is to point a second, freshly configured client at the same hostname and port with credentials typed in by hand. If that session authenticates, the fault is the first client's stored configuration and not the account. If the fresh client also stalls at 480 after sending AUTHINFO, the next code returned will identify the real problem, and it will be 481 or 502 rather than another 480.