{"record":{"id":"a700840f115df0b8","repo":"jstedfast/MailKit","slug":"no-credentials-could-be-found-for-the-imap-server-imapclient","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/ImapClient.cs","lineNumber":1352,"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\tengine.QueryCapabilities (cancellationToken);\n\n\t\t\t\t\tOnAuthenticated (ic.ResponseText ?? string.Empty, cancellationToken);\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\tengine.Run (ic);\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":1334,"sourceCodeEnd":1370,"githubUrl":"https://github.com/jstedfast/MailKit/blob/9d3859a7855e3e17582c07fd01972b8e262bf176/MailKit/Net/Imap/ImapClient.cs#L1334-L1370","documentation":"When SASL mechanisms fail or are unavailable, MailKit falls back to the classic LOGIN command using credentials from ICredentials.GetCredential(uri, \"DEFAULT\"). This AuthenticationException is thrown when that lookup returns null — i.e. the supplied ICredentials object has no credential matching the IMAP server URI for the default auth type.","triggerScenarios":"Calling Authenticate(uri, ICredentials) with a CredentialCache (or NetworkCredential-based ICredentials) that has no entry for the server URI/authType \"DEFAULT\", after SASL attempts did not apply, so GetCredential returns null.","commonSituations":"Passing an empty CredentialCache; registering credentials for a different URI prefix (http instead of imap) or wrong auth type string; using Windows-domain CredentialCache entries that don't match the IMAP host.","solutions":["Pass a NetworkCredential directly instead of a CredentialCache so GetCredential always resolves","If using CredentialCache, add an entry matching the exact uri and authType: cache.Add (uri, \"DEFAULT\", new NetworkCredential (user, pass))","Verify the Uri passed to Authenticate matches the one registered in the cache (scheme imap/imaps, host, port)","Check server capabilities and use a SASL mechanism (SaslMechanismLogin/OAuth2) rather than the ICredentials overload"],"exampleFix":"// before\nvar cache = new CredentialCache (); // no matching entry\ncache.Add (new Uri (\"http://mail.example.com\"), \"BASIC\", cred);\nclient.Authenticate (new Uri (\"imaps://mail.example.com\"), cache); // throws\n// after\nclient.Authenticate (new Uri (\"imaps://mail.example.com\"),\n    new NetworkCredential (user, pass));","handlingStrategy":"validation","validationCode":"var cred = credentials.GetCredential (uri, \"DEFAULT\"); if (cred == null) throw new InvalidOperationException ($\"No credential registered for {uri}\");","typeGuard":"null","tryCatchPattern":"try { client.Authenticate (uri, credentials); } catch (AuthenticationException ex) when (ex.Message.Contains (\"No credentials could be found\")) { // fix CredentialCache entry or pass NetworkCredential\n}","preventionTips":["Prefer NetworkCredential over CredentialCache for single-account apps","Ensure CredentialCache URI scheme/host/port exactly match the authenticate Uri","Use authType \"DEFAULT\" when registering cache entries","Consider SaslMechanism overloads to avoid the ICredentials path entirely"],"tags":["imap","credentials","authentication","mailkit"],"backgroundTag":"missing-credentials","analyzedSha":"9d3859a7855e3e17582c07fd01972b8e262bf176","analyzedAt":"2026-09-15T15:46:11.592Z","contentChangedAt":"2026-09-15T15:46:11.592Z","schemaVersion":2},"datasetVersion":"2026-09-15T23:17:13.987Z"}