diff --git a/src/main/java/kr/co/fastcampus/yanabada/common/security/oauth/Oauth2LoginSuccessHandler.java b/src/main/java/kr/co/fastcampus/yanabada/common/security/oauth/Oauth2LoginSuccessHandler.java
index ba786025..87f79600 100644
--- a/src/main/java/kr/co/fastcampus/yanabada/common/security/oauth/Oauth2LoginSuccessHandler.java
+++ b/src/main/java/kr/co/fastcampus/yanabada/common/security/oauth/Oauth2LoginSuccessHandler.java
@@ -51,7 +51,7 @@ public void onAuthenticationSuccess(
             authService.loginOauth(response, loginRequest, ProviderType.valueOf(provider));
         } else {
             /* 회원 가입 필요 */
-            String redirectUrl = appUrl
+            String redirectUrl = "https://www.yanabada.com"
                 + redirectPath
                 + "?email=" + email
                 + "&provider=" + provider;
diff --git a/src/main/java/kr/co/fastcampus/yanabada/domain/auth/controller/AuthController.java b/src/main/java/kr/co/fastcampus/yanabada/domain/auth/controller/AuthController.java
index 219a32b4..af9806da 100644
--- a/src/main/java/kr/co/fastcampus/yanabada/domain/auth/controller/AuthController.java
+++ b/src/main/java/kr/co/fastcampus/yanabada/domain/auth/controller/AuthController.java
@@ -16,6 +16,7 @@
 import kr.co.fastcampus.yanabada.domain.auth.dto.response.LoginResponse;
 import kr.co.fastcampus.yanabada.domain.auth.dto.response.SignUpResponse;
 import kr.co.fastcampus.yanabada.domain.auth.service.AuthService;
+import kr.co.fastcampus.yanabada.domain.member.dto.request.EmailDuplCheckRequest;
 import kr.co.fastcampus.yanabada.domain.member.dto.request.NickNameDuplCheckRequest;
 import kr.co.fastcampus.yanabada.domain.member.dto.response.DuplCheckResponse;
 import kr.co.fastcampus.yanabada.domain.member.service.MemberService;
@@ -77,6 +78,13 @@ public ResponseBody<TokenRefreshResponse> refreshToken(
         );
     }
 
+    @PostMapping("/duplication/email")
+    public ResponseBody<DuplCheckResponse> checkDuplEmail(
+        @RequestBody EmailDuplCheckRequest emailRequest
+    ) {
+        return ResponseBody.ok(memberService.isExistEmail(emailRequest));
+    }
+
     @PostMapping("/duplication/nickname")
     public ResponseBody<DuplCheckResponse> checkDuplNickName(
         @RequestBody NickNameDuplCheckRequest nickNameRequest
diff --git a/src/main/java/kr/co/fastcampus/yanabada/domain/chat/service/ChatService.java b/src/main/java/kr/co/fastcampus/yanabada/domain/chat/service/ChatService.java
index 27080430..23988b8e 100644
--- a/src/main/java/kr/co/fastcampus/yanabada/domain/chat/service/ChatService.java
+++ b/src/main/java/kr/co/fastcampus/yanabada/domain/chat/service/ChatService.java
@@ -125,7 +125,7 @@ private ChatRoomSummaryResponse createChatRoomSummaryResponse(
         return ChatRoomSummaryResponse.from(
             chatRoom.getCode(),
             partner,
-            messages.get(messages.size() - 1),
+            messages.get(0),
             chatRoom.getProduct(),
             unreadCount
         );
@@ -144,7 +144,7 @@ private List<ChatRoomSummaryResponse> sortChatRoomSummaryResponse(
             .sorted((cr1, cr2) -> {
                 LocalDateTime lastMessageTime1 = cr1.lastSentMessageTime();
                 LocalDateTime lastMessageTime2 = cr2.lastSentMessageTime();
-                return lastMessageTime1.compareTo(lastMessageTime2);
+                return lastMessageTime2.compareTo(lastMessageTime1);
             })
             .toList();
     }
diff --git a/src/main/java/kr/co/fastcampus/yanabada/domain/member/service/MemberService.java b/src/main/java/kr/co/fastcampus/yanabada/domain/member/service/MemberService.java
index 95d3fd47..d80e7a02 100644
--- a/src/main/java/kr/co/fastcampus/yanabada/domain/member/service/MemberService.java
+++ b/src/main/java/kr/co/fastcampus/yanabada/domain/member/service/MemberService.java
@@ -6,6 +6,7 @@
 import kr.co.fastcampus.yanabada.domain.auth.dto.request.EmailAuthRequest;
 import kr.co.fastcampus.yanabada.domain.auth.dto.response.EmailAuthResponse;
 import kr.co.fastcampus.yanabada.domain.auth.service.MailAuthService;
+import kr.co.fastcampus.yanabada.domain.member.dto.request.EmailDuplCheckRequest;
 import kr.co.fastcampus.yanabada.domain.member.dto.request.FcmTokenUpdateRequest;
 import kr.co.fastcampus.yanabada.domain.member.dto.request.NickNameDuplCheckRequest;
 import kr.co.fastcampus.yanabada.domain.member.dto.request.NickNameModifyRequest;
@@ -78,6 +79,15 @@ public EmailAuthResponse verifyEmail(
         return new EmailAuthResponse(mailAuthService.sendEmail(emailRequest.email()));
     }
 
+    @Transactional(readOnly = true)
+    public DuplCheckResponse isExistEmail(
+        EmailDuplCheckRequest emailRequest
+    ) {
+        boolean isExist = memberRepository
+            .existsByEmailAndProviderType(emailRequest.email(), EMAIL);
+        return new DuplCheckResponse(isExist);
+    }
+
     @Transactional(readOnly = true)
     public DuplCheckResponse isExistNickName(
         NickNameDuplCheckRequest nickNameRequest