diff --git a/rbox/billing/invoice_generator.py b/rbox/billing/invoice_generator.py
index 1f208e7..319b1f4 100644
--- a/rbox/billing/invoice_generator.py
+++ b/rbox/billing/invoice_generator.py
@@ -133,6 +133,50 @@ class InvoiceGenerator:
             except Exception as e:
                 print(f"Failed to finalize Stripe invoice: {e}")
 
+        # Send invoice email
+        from ..mail import queue_email
+        line_items = await invoice.line_items.all()
+        items_text = "\n".join([f"- {item.description}: ${item.amount}" for item in line_items])
+        body = f"""Dear {invoice.user.username},
+
+Your invoice {invoice.invoice_number} for the period {invoice.period_start} to {invoice.period_end} is now available.
+
+Invoice Details:
+{items_text}
+
+Subtotal: ${invoice.subtotal}
+Tax: ${invoice.tax}
+Total: ${invoice.total}
+
+Due Date: {invoice.due_date}
+
+You can view and pay your invoice at: {invoice.user.email}  # Placeholder, should be a link to invoice page
+
+Best regards,
+The RBox Team
+"""
+        html = f"""
+<h2>Invoice {invoice.invoice_number}</h2>
+<p>Dear {invoice.user.username},</p>
+<p>Your invoice for the period {invoice.period_start} to {invoice.period_end} is now available.</p>
+<table border="1">
+<tr><th>Description</th><th>Amount</th></tr>
+{"".join([f"<tr><td>{item.description}</td><td>${item.amount}</td></tr>" for item in line_items])}
+<tr><td><strong>Subtotal</strong></td><td><strong>${invoice.subtotal}</strong></td></tr>
+<tr><td><strong>Tax</strong></td><td><strong>${invoice.tax}</strong></td></tr>
+<tr><td><strong>Total</strong></td><td><strong>${invoice.total}</strong></td></tr>
+</table>
+<p>Due Date: {invoice.due_date}</p>
+<p>You can view and pay your invoice at: <a href="#">Invoice Link</a></p>
+<p>Best regards,<br>The RBox Team</p>
+"""
+        queue_email(
+            to_email=invoice.user.email,
+            subject=f"Your RBox Invoice {invoice.invoice_number}",
+            body=body,
+            html=html
+        )
+
         return invoice
 
     @staticmethod
diff --git a/rbox/mail.py b/rbox/mail.py
new file mode 100644
index 0000000..429f0e6
--- /dev/null
+++ b/rbox/mail.py
@@ -0,0 +1,105 @@
+import asyncio
+import aiosmtplib
+from email.mime.text import MIMEText
+from email.mime.multipart import MIMEMultipart
+from typing import Optional, Dict, Any
+from .settings import settings
+
+class EmailTask:
+    def __init__(self, to_email: str, subject: str, body: str, html: Optional[str] = None, **kwargs):
+        self.to_email = to_email
+        self.subject = subject
+        self.body = body
+        self.html = html
+        self.kwargs = kwargs
+
+class EmailService:
+    def __init__(self):
+        self.queue = asyncio.Queue()
+        self.worker_task: Optional[asyncio.Task] = None
+        self.running = False
+
+    async def start(self):
+        """Start the email worker"""
+        if self.running:
+            return
+        self.running = True
+        self.worker_task = asyncio.create_task(self._worker())
+
+    async def stop(self):
+        """Stop the email worker"""
+        if not self.running:
+            return
+        self.running = False
+        if self.worker_task:
+            self.worker_task.cancel()
+            try:
+                await self.worker_task
+            except asyncio.CancelledError:
+                pass
+
+    async def send_email(self, to_email: str, subject: str, body: str, html: Optional[str] = None, **kwargs):
+        """Queue an email for sending"""
+        task = EmailTask(to_email, subject, body, html, **kwargs)
+        await self.queue.put(task)
+
+    async def _worker(self):
+        """Email worker coroutine"""
+        while self.running:
+            try:
+                # Wait for a task with timeout to allow checking running flag
+                task = await asyncio.wait_for(self.queue.get(), timeout=1.0)
+                await self._send_email_task(task)
+                self.queue.task_done()
+            except asyncio.TimeoutError:
+                continue
+            except Exception as e:
+                # Log error, but continue processing
+                print(f"Email worker error: {e}")
+                continue
+
+    async def _send_email_task(self, task: EmailTask):
+        """Send a single email task"""
+        if not settings.SMTP_SERVER or not settings.SMTP_USERNAME or not settings.SMTP_PASSWORD:
+            print("SMTP not configured, skipping email send")
+            return
+
+        msg = MIMEMultipart('alternative')
+        msg['From'] = settings.SMTP_FROM_EMAIL
+        msg['To'] = task.to_email
+        msg['Subject'] = task.subject
+
+        # Add text part
+        text_part = MIMEText(task.body, 'plain')
+        msg.attach(text_part)
+
+        # Add HTML part if provided
+        if task.html:
+            html_part = MIMEText(task.html, 'html')
+            msg.attach(html_part)
+
+        try:
+            async with aiosmtplib.SMTP(
+                hostname=settings.SMTP_SERVER,
+                port=settings.SMTP_PORT,
+                username=settings.SMTP_USERNAME,
+                password=settings.SMTP_PASSWORD,
+                use_tls=True
+            ) as smtp:
+                await smtp.send_message(msg)
+                print(f"Email sent to {task.to_email}")
+        except Exception as e:
+            print(f"Failed to send email to {task.to_email}: {e}")
+            raise  # Re-raise to let caller handle
+
+# Global email service instance
+email_service = EmailService()
+
+# Convenience functions
+async def send_email(to_email: str, subject: str, body: str, html: Optional[str] = None, **kwargs):
+    """Send an email asynchronously"""
+    await email_service.send_email(to_email, subject, body, html, **kwargs)
+
+def queue_email(to_email: str, subject: str, body: str, html: Optional[str] = None, **kwargs):
+    """Queue an email for sending (fire and forget)"""
+    asyncio.create_task(email_service.send_email(to_email, subject, body, html, **kwargs))
\ No newline at end of file
diff --git a/rbox/main.py b/rbox/main.py
index 915368d..ef80848 100644
--- a/rbox/main.py
+++ b/rbox/main.py
@@ -20,8 +20,11 @@ async def lifespan(app: FastAPI):
     logger.info("Database connected.")
     from .billing.scheduler import start_scheduler
     from .billing.models import PricingConfig
+    from .mail import email_service
     start_scheduler()
     logger.info("Billing scheduler started")
+    await email_service.start()
+    logger.info("Email service started")
     pricing_count = await PricingConfig.all().count()
     if pricing_count == 0:
         from decimal import Decimal
@@ -38,6 +41,8 @@ async def lifespan(app: FastAPI):
     from .billing.scheduler import stop_scheduler
     stop_scheduler()
     logger.info("Billing scheduler stopped")
+    await email_service.stop()
+    logger.info("Email service stopped")
     print("Shutting down...")
 
 app = FastAPI(
diff --git a/rbox/routers/admin.py b/rbox/routers/admin.py
index 809043d..320861c 100644
--- a/rbox/routers/admin.py
+++ b/rbox/routers/admin.py
@@ -95,4 +95,15 @@ async def delete_user_by_admin(user_id: int):
     if not user:
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
     await user.delete()
-    return {"message": "User deleted successfully"}
\ No newline at end of file
+    return {"message": "User deleted successfully"}
+
+@router.post("/test-email")
+async def send_test_email(to_email: str, subject: str = "Test Email", body: str = "This is a test email"):
+    from ..mail import queue_email
+    queue_email(
+        to_email=to_email,
+        subject=subject,
+        body=body,
+        html=f"<h1>{subject}</h1><p>{body}</p>"
+    )
+    return {"message": "Test email queued"}
\ No newline at end of file
diff --git a/rbox/routers/auth.py b/rbox/routers/auth.py
index 90c0025..455f6fd 100644
--- a/rbox/routers/auth.py
+++ b/rbox/routers/auth.py
@@ -60,7 +60,16 @@ async def register_user(user_in: UserCreate):
         email=user_in.email,
         hashed_password=hashed_password,
     )
-    
+
+    # Send welcome email
+    from ..mail import queue_email
+    queue_email(
+        to_email=user.email,
+        subject="Welcome to RBox!",
+        body=f"Hi {user.username},\n\nWelcome to RBox! Your account has been created successfully.\n\nBest regards,\nThe RBox Team",
+        html=f"<h1>Welcome to RBox!</h1><p>Hi {user.username},</p><p>Welcome to RBox! Your account has been created successfully.</p><p>Best regards,<br>The RBox Team</p>"
+    )
+
     access_token_expires = timedelta(minutes=30) # Use settings
     access_token = create_access_token(
         data={"sub": user.username}, expires_delta=access_token_expires
diff --git a/requirements.txt b/requirements.txt
index 367c290..73fc17a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -118,3 +118,4 @@ watchfiles==1.1.1
 websockets==15.0.1
 yarl==1.22.0
 zstandard==0.25.0
+aiosmtplib==5.0.0