diff --git a/packages/backend/src/core/EmailService.ts b/packages/backend/src/core/EmailService.ts
index a176474b95..590d0ab64e 100644
--- a/packages/backend/src/core/EmailService.ts
+++ b/packages/backend/src/core/EmailService.ts
@@ -145,6 +145,7 @@ export class EmailService {
 		try {
 			// TODO: htmlサニタイズ
 			const info = await transporter.sendMail({
+				inReplyTo: this.meta.maintainerEmail ? { name: this.meta.maintainerName || 'Instance Maintainer', address: this.meta.maintainerEmail } : undefined,
 				from: this.meta.email!,
 				to: to,
 				subject: subject,