diff --git a/backend-node/src/controllers/mailAccountFileController.ts b/backend-node/src/controllers/mailAccountFileController.ts
index 702a5dd4..668dedf3 100644
--- a/backend-node/src/controllers/mailAccountFileController.ts
+++ b/backend-node/src/controllers/mailAccountFileController.ts
@@ -178,14 +178,19 @@ export class MailAccountFileController {
     try {
       const { id } = req.params;
       
-      // TODO: 실제 SMTP 연결 테스트 구현
-      // const account = await mailAccountFileService.getAccountById(id);
-      // nodemailer로 연결 테스트
+      const account = await mailAccountFileService.getAccountById(id);
+      if (!account) {
+        return res.status(404).json({
+          success: false,
+          message: '계정을 찾을 수 없습니다.',
+        });
+      }
 
-      return res.json({
-        success: true,
-        message: '연결 테스트 성공 (미구현)',
-      });
+      // mailSendSimpleService의 testConnection 사용
+      const { mailSendSimpleService } = require('../services/mailSendSimpleService');
+      const result = await mailSendSimpleService.testConnection(id);
+
+      return res.json(result);
     } catch (error: unknown) {
       const err = error as Error;
       return res.status(500).json({
diff --git a/backend-node/src/controllers/mailSendSimpleController.ts b/backend-node/src/controllers/mailSendSimpleController.ts
index cbd9b647..15a1bea0 100644
--- a/backend-node/src/controllers/mailSendSimpleController.ts
+++ b/backend-node/src/controllers/mailSendSimpleController.ts
@@ -7,10 +7,12 @@ export class MailSendSimpleController {
    */
   async sendMail(req: Request, res: Response) {
     try {
+      console.log('📧 메일 발송 요청 수신:', { accountId: req.body.accountId, to: req.body.to, subject: req.body.subject });
       const { accountId, templateId, to, subject, variables, customHtml } = req.body;
 
       // 필수 파라미터 검증
       if (!accountId || !to || !Array.isArray(to) || to.length === 0) {
+        console.log('❌ 필수 파라미터 누락');
         return res.status(400).json({
           success: false,
           message: '계정 ID와 수신자 이메일이 필요합니다.',
diff --git a/backend-node/src/services/mailSendSimpleService.ts b/backend-node/src/services/mailSendSimpleService.ts
index c5d2fc4f..473f3959 100644
--- a/backend-node/src/services/mailSendSimpleService.ts
+++ b/backend-node/src/services/mailSendSimpleService.ts
@@ -6,6 +6,7 @@
 import nodemailer from 'nodemailer';
 import { mailAccountFileService } from './mailAccountFileService';
 import { mailTemplateFileService } from './mailTemplateFileService';
+import { encryptionService } from './encryptionService';
 
 export interface SendMailRequest {
   accountId: string;
@@ -56,18 +57,39 @@ class MailSendSimpleService {
         throw new Error('메일 내용이 없습니다.');
       }
 
-      // 4. SMTP 연결 생성
+      // 4. 비밀번호 복호화
+      const decryptedPassword = encryptionService.decrypt(account.smtpPassword);
+      console.log('🔐 비밀번호 복호화 완료');
+      console.log('🔐 암호화된 비밀번호 (일부):', account.smtpPassword.substring(0, 30) + '...');
+      console.log('🔐 복호화된 비밀번호 길이:', decryptedPassword.length);
+
+      // 5. SMTP 연결 생성
+      // 포트 465는 SSL/TLS를 사용해야 함
+      const isSecure = account.smtpPort === 465 ? true : (account.smtpSecure || false);
+      
+      console.log('📧 SMTP 연결 설정:', {
+        host: account.smtpHost,
+        port: account.smtpPort,
+        secure: isSecure,
+        user: account.smtpUsername,
+      });
+
       const transporter = nodemailer.createTransport({
         host: account.smtpHost,
         port: account.smtpPort,
-        secure: account.smtpSecure, // SSL/TLS
+        secure: isSecure, // SSL/TLS (포트 465는 자동으로 true)
         auth: {
           user: account.smtpUsername,
-          pass: account.smtpPassword,
+          pass: decryptedPassword, // 복호화된 비밀번호 사용
         },
+        // 타임아웃 설정 (30초)
+        connectionTimeout: 30000,
+        greetingTimeout: 30000,
       });
 
-      // 5. 메일 발송
+      console.log('📧 메일 발송 시도 중...');
+
+      // 6. 메일 발송
       const info = await transporter.sendMail({
         from: `"${account.name}" <${account.email}>`,
         to: request.to.join(', '),
@@ -75,6 +97,12 @@ class MailSendSimpleService {
         html: htmlContent,
       });
 
+      console.log('✅ 메일 발송 성공:', {
+        messageId: info.messageId,
+        accepted: info.accepted,
+        rejected: info.rejected,
+      });
+
       return {
         success: true,
         messageId: info.messageId,
@@ -83,6 +111,8 @@ class MailSendSimpleService {
       };
     } catch (error) {
       const err = error as Error;
+      console.error('❌ 메일 발송 실패:', err.message);
+      console.error('❌ 에러 상세:', err);
       return {
         success: false,
         error: err.message,
@@ -178,22 +208,42 @@ class MailSendSimpleService {
    */
   async testConnection(accountId: string): Promise<{ success: boolean; message: string }> {
     try {
+      console.log('🔌 SMTP 연결 테스트 시작:', accountId);
+      
       const account = await mailAccountFileService.getAccountById(accountId);
       if (!account) {
         throw new Error('계정을 찾을 수 없습니다.');
       }
 
+      // 비밀번호 복호화
+      const decryptedPassword = encryptionService.decrypt(account.smtpPassword);
+      console.log('🔐 비밀번호 복호화 완료');
+
+      // 포트 465는 SSL/TLS를 사용해야 함
+      const isSecure = account.smtpPort === 465 ? true : (account.smtpSecure || false);
+
+      console.log('🔌 SMTP 연결 설정:', {
+        host: account.smtpHost,
+        port: account.smtpPort,
+        secure: isSecure,
+        user: account.smtpUsername,
+      });
+
       const transporter = nodemailer.createTransport({
         host: account.smtpHost,
         port: account.smtpPort,
-        secure: account.smtpSecure,
+        secure: isSecure,
         auth: {
           user: account.smtpUsername,
-          pass: account.smtpPassword,
+          pass: decryptedPassword, // 복호화된 비밀번호 사용
         },
+        connectionTimeout: 10000, // 10초 타임아웃
+        greetingTimeout: 10000,
       });
 
+      console.log('🔌 SMTP 연결 검증 중...');
       await transporter.verify();
+      console.log('✅ SMTP 연결 검증 성공!');
 
       return {
         success: true,
@@ -201,6 +251,7 @@ class MailSendSimpleService {
       };
     } catch (error) {
       const err = error as Error;
+      console.error('❌ SMTP 연결 실패:', err.message);
       return {
         success: false,
         message: `연결 실패: ${err.message}`,
diff --git a/frontend/app/(main)/admin/mail/accounts/page.tsx b/frontend/app/(main)/admin/mail/accounts/page.tsx
index 0171f2b6..ca0cf0b9 100644
--- a/frontend/app/(main)/admin/mail/accounts/page.tsx
+++ b/frontend/app/(main)/admin/mail/accounts/page.tsx
@@ -10,6 +10,7 @@ import {
   createMailAccount,
   updateMailAccount,
   deleteMailAccount,
+  testMailAccountConnection,
   CreateMailAccountDto,
   UpdateMailAccountDto,
 } from "@/lib/api/mail";
@@ -104,6 +105,24 @@ export default function MailAccountsPage() {
     }
   };
 
+  const handleTestConnection = async (account: MailAccount) => {
+    try {
+      setLoading(true);
+      const result = await testMailAccountConnection(account.id);
+      
+      if (result.success) {
+        alert(`✅ SMTP 연결 성공!\n\n${result.message || '정상적으로 연결되었습니다.'}`);
+      } else {
+        alert(`❌ SMTP 연결 실패\n\n${result.message || '연결에 실패했습니다.'}`);
+      }
+    } catch (error: any) {
+      console.error('연결 테스트 실패:', error);
+      alert(`❌ SMTP 연결 테스트 실패\n\n${error.message || '알 수 없는 오류가 발생했습니다.'}`);
+    } finally {
+      setLoading(false);
+    }
+  };
+
   return (
     <div className="min-h-screen bg-gray-50">
       <div className="w-full max-w-none px-4 py-8 space-y-8">
@@ -148,6 +167,7 @@ export default function MailAccountsPage() {
                 onEdit={handleOpenEditModal}
                 onDelete={handleOpenDeleteModal}
                 onToggleStatus={handleToggleStatus}
+                onTestConnection={handleTestConnection}
               />
             </CardContent>
           </Card>
diff --git a/frontend/components/mail/MailAccountTable.tsx b/frontend/components/mail/MailAccountTable.tsx
index da929373..ec88a466 100644
--- a/frontend/components/mail/MailAccountTable.tsx
+++ b/frontend/components/mail/MailAccountTable.tsx
@@ -21,6 +21,7 @@ interface MailAccountTableProps {
   onEdit: (account: MailAccount) => void;
   onDelete: (account: MailAccount) => void;
   onToggleStatus: (account: MailAccount) => void;
+  onTestConnection: (account: MailAccount) => void;
 }
 
 export default function MailAccountTable({
@@ -28,6 +29,7 @@ export default function MailAccountTable({
   onEdit,
   onDelete,
   onToggleStatus,
+  onTestConnection,
 }: MailAccountTableProps) {
   const [searchTerm, setSearchTerm] = useState('');
   const [sortField, setSortField] = useState<keyof MailAccount>('createdAt');
@@ -220,6 +222,13 @@ export default function MailAccountTable({
                   </td>
                   <td className="px-6 py-4">
                     <div className="flex items-center justify-center gap-2">
+                      <button
+                        onClick={() => onTestConnection(account)}
+                        className="p-2 text-blue-600 hover:bg-blue-50 rounded-lg transition-colors"
+                        title="SMTP 연결 테스트"
+                      >
+                        <Zap className="w-4 h-4" />
+                      </button>
                       <button
                         onClick={() => onEdit(account)}
                         className="p-2 text-primary hover:bg-accent rounded-lg transition-colors"
diff --git a/frontend/lib/api/mail.ts b/frontend/lib/api/mail.ts
index e9e44fb8..5d6862b6 100644
--- a/frontend/lib/api/mail.ts
+++ b/frontend/lib/api/mail.ts
@@ -168,6 +168,15 @@ export async function deleteMailAccount(id: string): Promise<{ success: boolean
   });
 }
 
+/**
+ * SMTP 연결 테스트
+ */
+export async function testMailAccountConnection(id: string): Promise<{ success: boolean; message: string }> {
+  return fetchApi<{ success: boolean; message: string }>(`/accounts/${id}/test-connection`, {
+    method: 'POST',
+  });
+}
+
 /**
  * SMTP 연결 테스트
  */