/**
 * Structured logging for the Email MCP server.
 *
 * As of MCP 2026-07-28 the `logging` capability and the server→client
 * `notifications/message` channel are deprecated (SEP-2577). For a stdio
 * server the correct, always-safe sink is **stderr**: it never pollutes the
 * JSON-RPC stream on stdout, needs no handshake gating, and is surfaced by
 * MCP clients (Claude Desktop, Cursor, …) as server logs.
 *
 * `mcpLog()` keeps its original fire-and-forget `Promise<void>` signature so
 * the many existing call sites (`await mcpLog(…)` and `mcpLog(…).catch(…)`)
 * are unchanged.
 */
export type LogLevel = 'debug' | 'info' | 'notice' | 'warning' | 'error' | 'critical' | 'alert' | 'emergency';
/**
 * Emit a structured log line to stderr.
 *
 * Safe to call anywhere, at any time — stderr is always protocol-safe for
 * stdio transports, so there is no pre-handshake window to guard against.
 */
export declare function mcpLog(level: LogLevel, logger: string, data: unknown): Promise<void>;
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