{"record":{"id":"3abc9f17a3f7f774","repo":"jstedfast/MailKit","slug":"no-credentials-could-be-found-for-the-imap-server","errorCode":null,"errorMessage":"No credentials could be found for the IMAP server.","messagePattern":"No credentials could be found for the IMAP server\\.","errorType":"exception","errorClass":"AuthenticationException","httpStatus":null,"severity":"error","filePath":"MailKit/Net/Imap/AsyncImapClient.cs","lineNumber":472,"sourceCode":"\t\t\t\t\tif (id != identifier) {\n\t\t\t\t\t\tengine.FolderCache.Clear ();\n\t\t\t\t\t\tidentifier = id;\n\t\t\t\t\t}\n\n\t\t\t\t\t// Query the CAPABILITIES again if the server did not include an\n\t\t\t\t\t// untagged CAPABILITIES response to the AUTHENTICATE command.\n\t\t\t\t\tif (engine.CapabilitiesVersion == capabilitiesVersion)\n\t\t\t\t\t\tawait engine.QueryCapabilitiesAsync (cancellationToken).ConfigureAwait (false);\n\n\t\t\t\t\tawait OnAuthenticatedAsync (ic.ResponseText ?? string.Empty, cancellationToken).ConfigureAwait (false);\n\t\t\t\t\treturn;\n\t\t\t\t}\n\n\t\t\t\tCheckCanLogin (ic);\n\n\t\t\t\t// fall back to the classic LOGIN command...\n\t\t\t\tif ((cred = credentials.GetCredential (uri, \"DEFAULT\")) == null)\n\t\t\t\t\tthrow new AuthenticationException (\"No credentials could be found for the IMAP server.\");\n\n\t\t\t\tic = engine.QueueCommand (cancellationToken, null, \"LOGIN %S %S\\r\\n\", cred.UserName, cred.Password);\n\n\t\t\t\tdetector.IsAuthenticating = true;\n\n\t\t\t\ttry {\n\t\t\t\t\tawait engine.RunAsync (ic).ConfigureAwait (false);\n\t\t\t\t} finally {\n\t\t\t\t\tdetector.IsAuthenticating = false;\n\t\t\t\t}\n\n\t\t\t\tif (ic.Response != ImapCommandResponse.Ok)\n\t\t\t\t\tthrow CreateAuthenticationException (ic);\n\n\t\t\t\tengine.State = ImapEngineState.Authenticated;\n\n\t\t\t\tid = GetSessionIdentifier (cred.UserName);\n\t\t\t\tif (id != identifier) {","sourceCodeStart":454,"sourceCodeEnd":490,"githubUrl":"https://github.com/jstedfast/MailKit/blob/9d3859a7855e3e17582c07fd01972b8e262bf176/MailKit/Net/Imap/AsyncImapClient.cs#L454-L490","documentation":"During IMAP authentication, after SASL mechanisms are exhausted, ImapClient falls back to the classic LOGIN command and looks up credentials via the supplied ICredentials.GetCredential(uri, \"DEFAULT\"). If that returns null, no credentials are available at all, so an AuthenticationException is thrown.","triggerScenarios":"Calling ImapClient.Authenticate ICredentials whose GetCredential returns null for the server's host/port/authType (e.g. NetworkCredential created empty, or a custom ICredentials that does not match the URI).","commonSituations":"Using CredentialCache with credentials registered for the wrong host/port; a custom credential store that has no entry for this server; credentials cleared or not loaded from a secrets store at runtime.","solutions":["Verify the ICredentials implementation returns a non-null NetworkCredential for the server URI","If using CredentialCache, register the credential for the exact host, port, and auth type used to connect","Load credentials (user/password) before connecting and pass them via Authenticate(user, password) instead of the ICredentials overload"],"exampleFix":"// before\nclient.Connect(uri);\nclient.Authenticate(credentials); // CredentialCache has no entry for this host\n// after\nclient.Connect(uri);\nclient.Authenticate(\"user@example.com\", \"app-password\");","handlingStrategy":"validation","validationCode":"var cred = credentials.GetCredential(uri, \"DEFAULT\");\nif (cred == null || string.IsNullOrEmpty(cred.UserName))\n\tthrow new InvalidOperationException($\"No credential registered for {uri.Host}:{uri.Port}\");","typeGuard":"bool HasCredential(ICredentials creds, Uri uri) => creds?.GetCredential(uri, \"DEFAULT\") != null;","tryCatchPattern":"try {\n\tawait client.AuthenticateAsync(credentials);\n} catch (AuthenticationException ex) {\n\t// log which host/uri lacked credentials, load from secret store and retry once\n}","preventionTips":["Prefer Authenticate(user, password) with explicitly loaded secrets over CredentialCache","When using CredentialCache, register for the exact host, port, and authType","Fail fast at startup if required credentials are absent from the environment/secrets store"],"tags":["imap","authentication","credentials","network"],"backgroundTag":"missing-credentials","analyzedSha":"9d3859a7855e3e17582c07fd01972b8e262bf176","analyzedAt":"2026-09-15T15:46:11.592Z","contentChangedAt":"2026-09-15T15:46:11.592Z","schemaVersion":2},"datasetVersion":"2026-09-16T04:17:20.429Z"}