diff --git a/server/api/public/profile/[publicSlug]/posts/[postSlug]/comments.post.ts b/server/api/public/profile/[publicSlug]/posts/[postSlug]/comments.post.ts
index a95fa4e..4f69a2a 100644
--- a/server/api/public/profile/[publicSlug]/posts/[postSlug]/comments.post.ts
+++ b/server/api/public/profile/[publicSlug]/posts/[postSlug]/comments.post.ts
@@ -1,6 +1,7 @@
 import { getRequestIP } from "h3";
 import { getPublicPostCommentContext } from "#server/service/posts";
 import { createComment } from "#server/service/post-comments";
+import { notifyReplyCommentCreated } from "#server/service/comment-notify";
 import { assertUnderRateLimit } from "#server/utils/simple-rate-limit";
 import { parsePublicPostCreateCommentBody } from "#server/api/public/comments-create-body";
 
@@ -45,5 +46,11 @@ export default defineEventHandler(async (event) => {
     body: parsed.body,
   });
 
+  void notifyReplyCommentCreated({
+    parentId: parsed.parentId,
+    actorUserId: viewer?.id ?? null,
+    replyBody: parsed.body,
+  });
+
   return R.success({ id: newCommentId });
 });
diff --git a/server/api/public/unlisted/[publicSlug]/[shareToken]/comments.post.ts b/server/api/public/unlisted/[publicSlug]/[shareToken]/comments.post.ts
index c931c71..193e566 100644
--- a/server/api/public/unlisted/[publicSlug]/[shareToken]/comments.post.ts
+++ b/server/api/public/unlisted/[publicSlug]/[shareToken]/comments.post.ts
@@ -1,6 +1,7 @@
 import { getRequestIP } from "h3";
 import { getUnlistedPostCommentContext } from "#server/service/posts";
 import { createComment } from "#server/service/post-comments";
+import { notifyReplyCommentCreated } from "#server/service/comment-notify";
 import { assertUnderRateLimit } from "#server/utils/simple-rate-limit";
 import { parseUnlistedCreateCommentBody } from "#server/api/public/comments-create-body";
 
@@ -45,5 +46,11 @@ export default defineEventHandler(async (event) => {
     body: parsed.body,
   });
 
+  void notifyReplyCommentCreated({
+    parentId: parsed.parentId,
+    actorUserId: viewer?.id ?? null,
+    replyBody: parsed.body,
+  });
+
   return R.success({ id: newCommentId });
 });
diff --git a/server/service/comment-notify/index.test.ts b/server/service/comment-notify/index.test.ts
new file mode 100644
index 0000000..4c46c9b
--- /dev/null
+++ b/server/service/comment-notify/index.test.ts
@@ -0,0 +1,78 @@
+import { describe, expect, test } from "bun:test";
+import { notifyReplyCommentCreated } from "./index";
+
+function createDeps() {
+  const state = {
+    sendMailCalled: false,
+  };
+
+  return {
+    state,
+    deps: {
+      getParentAuthorUserId: async () => 2,
+      getGlobalConfig: async () => ({
+        enabled: true,
+        fromEmail: "noreply@example.com",
+        smtpHost: "smtp.example.com",
+        smtpPort: 465,
+        smtpSecure: true,
+        smtpUser: "smtp-user",
+        smtpPass: "smtp-pass",
+      }),
+      getReceiverNotifyEnabled: async () => true,
+      getReceiverProfile: async () => ({
+        email: "receiver@example.com",
+        username: "receiver",
+        nickname: "Receiver",
+      }),
+      sendMail: async () => {
+        state.sendMailCalled = true;
+      },
+    },
+  };
+}
+
+describe("notifyReplyCommentCreated", () => {
+  test("全局开关关闭 -> 不发送", async () => {
+    const { deps, state } = createDeps();
+    deps.getGlobalConfig = async () => ({
+      enabled: false,
+      fromEmail: "noreply@example.com",
+      smtpHost: "smtp.example.com",
+      smtpPort: 465,
+      smtpSecure: true,
+      smtpUser: "smtp-user",
+      smtpPass: "smtp-pass",
+    });
+
+    await notifyReplyCommentCreated({ parentId: 100, actorUserId: 1, replyBody: "hello" }, deps);
+
+    expect(state.sendMailCalled).toBe(false);
+  });
+
+  test("用户偏好关闭 -> 不发送", async () => {
+    const { deps, state } = createDeps();
+    deps.getReceiverNotifyEnabled = async () => false;
+
+    await notifyReplyCommentCreated({ parentId: 100, actorUserId: 1, replyBody: "hello" }, deps);
+
+    expect(state.sendMailCalled).toBe(false);
+  });
+
+  test("无 parentId -> 不发送", async () => {
+    const { deps, state } = createDeps();
+
+    await notifyReplyCommentCreated({ parentId: null, actorUserId: 1, replyBody: "hello" }, deps);
+
+    expect(state.sendMailCalled).toBe(false);
+  });
+
+  test("自通知 -> 不发送", async () => {
+    const { deps, state } = createDeps();
+    deps.getParentAuthorUserId = async () => 1;
+
+    await notifyReplyCommentCreated({ parentId: 100, actorUserId: 1, replyBody: "hello" }, deps);
+
+    expect(state.sendMailCalled).toBe(false);
+  });
+});
diff --git a/server/service/comment-notify/index.ts b/server/service/comment-notify/index.ts
new file mode 100644
index 0000000..44d8e44
--- /dev/null
+++ b/server/service/comment-notify/index.ts
@@ -0,0 +1,184 @@
+import log4js from "logger";
+import nodemailer from "nodemailer";
+
+const logger = log4js.getLogger("COMMENT_NOTIFY");
+
+type NotifyGlobalConfig = {
+  enabled: boolean;
+  fromEmail: string;
+  smtpHost: string;
+  smtpPort: number;
+  smtpSecure: boolean;
+  smtpUser: string;
+  smtpPass: string;
+};
+
+type ReceiverProfile = {
+  email: string | null;
+  username: string | null;
+  nickname: string | null;
+};
+
+type NotifyDeps = {
+  getParentAuthorUserId: (parentId: number) => Promise<number | null>;
+  getGlobalConfig: () => Promise<NotifyGlobalConfig>;
+  getReceiverNotifyEnabled: (userId: number) => Promise<boolean>;
+  getReceiverProfile: (userId: number) => Promise<ReceiverProfile | null>;
+  sendMail: (input: { toEmail: string; fromEmail: string; replyBody: string }) => Promise<void>;
+};
+
+function hasValue(value: string): boolean {
+  return value.trim().length > 0;
+}
+
+function isSmtpConfigReady(config: NotifyGlobalConfig): boolean {
+  return (
+    config.enabled &&
+    hasValue(config.fromEmail) &&
+    hasValue(config.smtpHost) &&
+    hasValue(config.smtpUser) &&
+    hasValue(config.smtpPass) &&
+    Number.isInteger(config.smtpPort) &&
+    config.smtpPort >= 1 &&
+    config.smtpPort <= 65535
+  );
+}
+
+async function defaultGetParentAuthorUserId(parentId: number): Promise<number | null> {
+  const { dbGlobal } = await import("drizzle-pkg/lib/db");
+  const { postComments } = await import("drizzle-pkg/lib/schema/content");
+  const { eq } = await import("drizzle-orm");
+
+  const [parent] = await dbGlobal
+    .select({
+      authorUserId: postComments.authorUserId,
+    })
+    .from(postComments)
+    .where(eq(postComments.id, parentId))
+    .limit(1);
+
+  return parent?.authorUserId ?? null;
+}
+
+async function defaultGetGlobalConfig(): Promise<NotifyGlobalConfig> {
+  const { getGlobalConfigValue } = await import("../config");
+
+  return {
+    enabled: await getGlobalConfigValue("commentEmailNotifyEnabled"),
+    fromEmail: await getGlobalConfigValue("commentMailFromEmail"),
+    smtpHost: await getGlobalConfigValue("commentSmtpHost"),
+    smtpPort: await getGlobalConfigValue("commentSmtpPort"),
+    smtpSecure: await getGlobalConfigValue("commentSmtpSecure"),
+    smtpUser: await getGlobalConfigValue("commentSmtpUser"),
+    smtpPass: await getGlobalConfigValue("commentSmtpPass"),
+  };
+}
+
+async function defaultGetReceiverNotifyEnabled(userId: number): Promise<boolean> {
+  const { getMergedConfigValue } = await import("../config");
+  return getMergedConfigValue(userId, "commentNotifyEnabled");
+}
+
+async function defaultGetReceiverProfile(userId: number): Promise<ReceiverProfile | null> {
+  const { dbGlobal } = await import("drizzle-pkg/lib/db");
+  const { users } = await import("drizzle-pkg/lib/schema/auth");
+  const { eq } = await import("drizzle-orm");
+
+  const [user] = await dbGlobal
+    .select({
+      email: users.email,
+      username: users.username,
+      nickname: users.nickname,
+    })
+    .from(users)
+    .where(eq(users.id, userId))
+    .limit(1);
+  return user ?? null;
+}
+
+async function defaultSendMail(input: { toEmail: string; fromEmail: string; replyBody: string }): Promise<void> {
+  const { getGlobalConfigValue } = await import("../config");
+
+  const smtpHost = await getGlobalConfigValue("commentSmtpHost");
+  const smtpPort = await getGlobalConfigValue("commentSmtpPort");
+  const smtpSecure = await getGlobalConfigValue("commentSmtpSecure");
+  const smtpUser = await getGlobalConfigValue("commentSmtpUser");
+  const smtpPass = await getGlobalConfigValue("commentSmtpPass");
+
+  const transporter = nodemailer.createTransport({
+    host: smtpHost,
+    port: smtpPort,
+    secure: smtpSecure,
+    connectionTimeout: 10_000,
+    greetingTimeout: 10_000,
+    socketTimeout: 15_000,
+    auth: {
+      user: smtpUser,
+      pass: smtpPass,
+    },
+  });
+
+  await transporter.sendMail({
+    from: input.fromEmail,
+    to: input.toEmail.trim(),
+    subject: "[Person Panel] 你收到一条评论回复",
+    text: `你收到了一条新的评论回复。\n\n回复内容：\n${input.replyBody}\n`,
+  });
+}
+
+function getDefaultDeps(): NotifyDeps {
+  return {
+    getParentAuthorUserId: defaultGetParentAuthorUserId,
+    getGlobalConfig: defaultGetGlobalConfig,
+    getReceiverNotifyEnabled: defaultGetReceiverNotifyEnabled,
+    getReceiverProfile: defaultGetReceiverProfile,
+    sendMail: defaultSendMail,
+  };
+}
+
+export async function notifyReplyCommentCreated(
+  input: {
+    parentId: number | null;
+    actorUserId: number | null;
+    replyBody: string;
+  },
+  deps: NotifyDeps = getDefaultDeps(),
+): Promise<void> {
+  try {
+    if (input.parentId == null) {
+      return;
+    }
+
+    const receiverUserId = await deps.getParentAuthorUserId(input.parentId);
+    if (receiverUserId == null) {
+      return;
+    }
+
+    if (input.actorUserId != null && input.actorUserId === receiverUserId) {
+      return;
+    }
+
+    const globalConfig = await deps.getGlobalConfig();
+    if (!isSmtpConfigReady(globalConfig)) {
+      return;
+    }
+
+    const receiverNotifyEnabled = await deps.getReceiverNotifyEnabled(receiverUserId);
+    if (!receiverNotifyEnabled) {
+      return;
+    }
+
+    const receiver = await deps.getReceiverProfile(receiverUserId);
+    if (!receiver?.email || !hasValue(receiver.email)) {
+      return;
+    }
+
+    await deps.sendMail({
+      toEmail: receiver.email,
+      fromEmail: globalConfig.fromEmail,
+      replyBody: input.replyBody,
+    });
+  } catch (error) {
+    logger.warn("failed to send reply comment notify email", error);
+  }
+}