diff --git a/src/auth/guards/rate-limit.guard.ts b/src/auth/guards/rate-limit.guard.ts
index ce5d740..a591e1f 100644
--- a/src/auth/guards/rate-limit.guard.ts
+++ b/src/auth/guards/rate-limit.guard.ts
@@ -52,15 +52,16 @@ export class RateLimitGuard implements CanActivate {
     const endpoint = `${request.method} ${request.route?.path || request.url}`;
 
     try {
-      // Check by user if authenticated
+      const ip = this.getClientIp(request);
+
       if (request.user?.id) {
         const userTier = request.user.tier || 'free';
-        const userStatus = await this.rateLimitService.checkUserRateLimit(
-          request.user.id,
-          userTier,
-        );
 
-        // Apply rate limit headers
+        const [userStatus, userIpStatus] = await Promise.all([
+          this.rateLimitService.checkUserRateLimit(request.user.id, userTier),
+          this.rateLimitService.checkUserIpRateLimit(request.user.id, ip),
+        ]);
+
         Object.entries(this.rateLimitService.getHeaders(userStatus)).forEach(([key, value]) => {
           response.setHeader(key, value);
         });
@@ -73,17 +74,24 @@ export class RateLimitGuard implements CanActivate {
               retryAfter: userStatus.retryAfter,
             },
             HttpStatus.TOO_MANY_REQUESTS,
+            { cause: 'user_rate_limit_exceeded' },
+          );
+        }
+
+        if (userIpStatus.isExceeded) {
+          throw new HttpException(
             {
-              cause: 'user_rate_limit_exceeded',
+              statusCode: HttpStatus.TOO_MANY_REQUESTS,
+              message: 'Too many requests from this account on this IP. Please try again later.',
+              retryAfter: userIpStatus.retryAfter,
             },
+            HttpStatus.TOO_MANY_REQUESTS,
+            { cause: 'user_ip_rate_limit_exceeded' },
           );
         }
       } else {
-        // Check by IP for unauthenticated requests
-        const ip = this.getClientIp(request);
         const ipStatus = await this.rateLimitService.checkIpRateLimit(ip);
 
-        // Apply rate limit headers
         Object.entries(this.rateLimitService.getHeaders(ipStatus)).forEach(([key, value]) => {
           response.setHeader(key, value);
         });
@@ -96,9 +104,7 @@ export class RateLimitGuard implements CanActivate {
               retryAfter: ipStatus.retryAfter,
             },
             HttpStatus.TOO_MANY_REQUESTS,
-            {
-              cause: 'ip_rate_limit_exceeded',
-            },
+            { cause: 'ip_rate_limit_exceeded' },
           );
         }
       }
diff --git a/src/auth/rate-limit.config.ts b/src/auth/rate-limit.config.ts
index 6b70d74..bd1b0e2 100644
--- a/src/auth/rate-limit.config.ts
+++ b/src/auth/rate-limit.config.ts
@@ -146,6 +146,7 @@ export const RATE_LIMIT_KEYS = {
   ENDPOINT: (endpoint: string) => `rate-limit:endpoint:${endpoint}`,
   USER: (userId: string) => `rate-limit:user:${userId}`,
   IP: (ip: string) => `rate-limit:ip:${ip}`,
+  USER_IP: (userId: string, ip: string) => `rate-limit:user-ip:${userId}:${ip}`,
   API_KEY: (apiKey: string) => `rate-limit:api-key:${apiKey}`,
 };
 
diff --git a/src/auth/rate-limit.service.ts b/src/auth/rate-limit.service.ts
index 7494309..e4be5c8 100644
--- a/src/auth/rate-limit.service.ts
+++ b/src/auth/rate-limit.service.ts
@@ -169,6 +169,18 @@ export class RateLimitService {
     await this.cacheManager.del(key);
   }
 
+  /**
+   * Check rate limit for a user tied to a specific IP
+   * Prevents abuse from multiple accounts on the same IP or a single user hopping IPs
+   */
+  async checkUserIpRateLimit(userId: string, ip: string): Promise<RateLimitStatus> {
+    const key = RATE_LIMIT_KEYS.USER_IP(userId, ip);
+    const limit = 200; // Combined user+IP limit
+    const windowMs = 15 * 60 * 1000; // 15 minutes
+
+    return this.checkRateLimit(key, limit, windowMs);
+  }
+
   /**
    * Get rate limit status with headers
    */
diff --git a/src/email/email.module.ts b/src/email/email.module.ts
index 0e53277..3aff01d 100644
--- a/src/email/email.module.ts
+++ b/src/email/email.module.ts
@@ -18,6 +18,13 @@ import { EmailProcessor } from './email.processor';
     TrackingModule,
     BullModule.registerQueue({
       name: 'mail',
+      defaultJobOptions: {
+        attempts: 3,
+        backoff: {
+          type: 'exponential',
+          delay: 1000,
+        },
+      },
     }),
     MailerModule.forRootAsync({
       useFactory: (config: ConfigService) => ({
diff --git a/src/main.ts b/src/main.ts
index 440e6e4..02895fd 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -12,8 +12,10 @@ import { RateLimitGuard } from './auth/guards/rate-limit.guard';
 import { RateLimitService } from './auth/rate-limit.service';
 import { RateLimitHeadersInterceptor } from './auth/interceptors/rate-limit-headers.interceptor';
 import { setupSwagger } from './config/swagger.config';
+import { validateEnvironment } from './utils/validate-env';
 
 async function bootstrap() {
+  validateEnvironment();
   const app = await NestFactory.create(AppModule);
   const logger = new Logger('Bootstrap');
 
diff --git a/src/utils/validate-env.ts b/src/utils/validate-env.ts
new file mode 100644
index 0000000..5b1f866
--- /dev/null
+++ b/src/utils/validate-env.ts
@@ -0,0 +1,24 @@
+const REQUIRED_ENV_VARS = [
+  'DATABASE_URL',
+  'JWT_SECRET',
+  'JWT_REFRESH_SECRET',
+] as const;
+
+export function validateEnvironment(): void {
+  const MISSING: string[] = [];
+
+  for (const key of REQUIRED_ENV_VARS) {
+    if (!process.env[key]) {
+      MISSING.push(key);
+    }
+  }
+
+  if (MISSING.length > 0) {
+    console.error(
+      `\n  Fatal: Missing required environment variables:\n` +
+        MISSING.map((k) => `    - ${k}`).join('\n') +
+        `\n\n  Please set them in .env or .env.local before starting the application.\n`,
+    );
+    process.exit(1);
+  }
+}