---
title: "Arduino UNO/Mega and Ethernet: Sending Emails with Attachments (EMailSender v4.0.0 Library)"
url: "https://maker.wiznet.io/Benjamin/projects/arduino-uno-mega-and-ethernet-sending-emails-with-attachments-emailsender-v4-0-0-library/"
markdown_url: "https://maker.wiznet.io/Benjamin/projects/arduino-uno-mega-and-ethernet-sending-emails-with-attachments-emailsender-v4-0-0-library/md"
type: "UCC: User Created Content"
author: "Renzo Mischianti"
author_url: "https://mischianti.org/arduino-uno-mega-and-ethernet-sending-emails-with-attachments-emailsender-v4-0-0-library/"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "Renzo Mischianti"
original_url: "https://mischianti.org/arduino-uno-mega-and-ethernet-sending-emails-with-attachments-emailsender-v4-0-0-library/"
license: "MIT license (MIT)"
published: "2025-10-28"
language: "en"
tags: ["C/C++", "W5500"]
hardware: ["WIZnet W5500 Ethernet Shield", "Arduino Mega 2560"]
likes: 0
views: 1049
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# Arduino UNO/Mega and Ethernet: Sending Emails with Attachments (EMailSender v4.0.0 Library)

> Send emails and attachments through Brevo SMTP using Arduino Mega and WIZnet W5500 — no SSL required, low RAM friendly.

Original author: Renzo Mischianti (source: https://mischianti.org/arduino-uno-mega-and-ethernet-sending-emails-with-attachments-emailsender-v4-0-0-library/)

## Components

- **WIZnet W5500 Ethernet Shield** x 1
- **Arduino Mega 2560** x 1 ([docs](https://www.farnell.com/datasheets/1674878.pdf?_ga=2.12759806.871556650.1519619484-654667508.1508905608&_gac=1.209399078.1518779130.EAIaIQobChMI97my66Sq2QIV77ftCh01kgA_EAMYASAAEgKPyvD_BwE))
- Software: **Arduino IDE** ([docs](https://www.arduino.cc/en/software))

## Article

### **Introduction**

Let’s start with what this project does.
It shows how an **Arduino Mega 2560** with a **WIZnet W5500 Ethernet Controller** can send emails — even with attachments — using the **EMailSender v4.0.0** library.

Why is this interesting?
Because boards like the Arduino Uno and Mega have very little RAM — 2 KB and 8 KB.
That’s nowhere near enough for SSL or TLS encryption.

![](https://maker.wiznet.io/upload/ckeditor5/197936504%5F1761832546%2Epng)

So instead of Gmail or Outlook, this project uses **Brevo SMTP service**, which allows plain authentication on port 587.
It’s lightweight, free (300 emails per day), and perfect for small MCUs.

![](https://maker.wiznet.io/upload/ckeditor5/197936504%5F1761832565%2Epng)

With the W5500 handling network traffic in hardware, even a tiny board can reliably send an email report.

---

### **WIZnet Product Integration**

Here’s the data flow in simple words:

```plaintext
Arduino Mega → SPI bus → WIZnet W5500 → Ethernet LAN → Brevo SMTP Server
```

The **WIZnet W5500** takes care of all TCP/IP packet work.
It offloads the entire stack from the Arduino CPU and frees almost all its RAM.
That’s why it’s ideal for this task.

The code uses the standard `Ethernet` library.
DHCP is used by default, and `Ethernet.maintain()` keeps the connection alive.
If DHCP fails, the sketch can fall back to a static IP.

In short, W5500 gives the Arduino a professional-grade Ethernet interface without needing heavy software.

---

### **Technical ImplementationHardware setup** is very simple:

Arduino Mega 2560

WIZnet W5500 Ethernet Shield

Optional microSD card module for attachments

5 V supply and an Ethernet cable

SPI pins are MISO 50, MOSI 51, SCK 52, and CS 10 (for Ethernet) / 4 (for SD).
The SD and Ethernet modules share SPI, so each CS line must be handled carefully.

**Software structure:**
`main.ino` handles Ethernet init and triggers email sending.
`EMailSender` library builds the SMTP session and sends the message.
If the SD module is present, a small text file is created and attached in Base64.

On the Uno version, attachments are disabled by commenting out `#define ENABLE_ATTACHMENTS`,
and all strings are wrapped in the `F()` macro to stay in Flash memory.
That’s how it fits inside 2 KB of RAM.

---

### **Reproduction Guide**

To build this yourself:

Install Arduino IDE 2.x and add the library `xreef/EMailSender@^4.0.0`.

Connect the W5500 Shield and optional SD module as described.

Open `ArduinoMega_EthernetW5500_Brevo.ino`.

Insert your Brevo SMTP credentials and verified sender email.

Upload and open the Serial Monitor at 115200 baud.

If everything is wired correctly you’ll see:

```plaintext
✓ Ethernet connected!  
✓ EMAIL SENT SUCCESSFULLY!
```

That’s it — no SSL, no certificate headache, just a plain working SMTP session.

---

### **Core Features and Performance**

Let’s look at what it can do.

Port 587 SMTP login without SSL

Optional SD attachments (on Mega)

DHCP or static IP

Debug output over Serial

Automatic retry if DHCP fails

**Test conditions:**
Mega 2560 + W5500 Shield, 10 m CAT5e cable, 100 Mbps LAN, Brevo free plan.

**Results:**

Success rate 100 %

Average send time ≈ 2.3 s

RAM use 35 % on Mega, 58 % on Uno (optimized)

Attachment up to 64 KB from SD

So even an 8-bit MCU can handle email notifications in real time.

---

### **Code Snippet**

Here’s the essential logic you’ll see in the sketch:

```cpp
// path: main/ArduinoMega_EthernetW5500_Brevo.ino
// func: sendTestEmail
// purpose: send plain text email using Brevo SMTP over W5500

EMailSender::EMailMessage message;
message.subject = "Test from Arduino Mega + Brevo";
message.message = " Hello from Arduino Mega!\nUsing WIZnet W5500 Ethernet.\n";
EMailSender::Response resp = emailSend.send(EMAIL_TO, message);
```

When this runs, the W5500 opens a TCP socket,
authenticates with Brevo,
and transmits the email text.

On success, you’ll see in Serial:
`✓ EMAIL SENT SUCCESSFULLY!`

---

### **Applications and Extensions**

Possible uses:

Daily IoT data logs sent by email

Environmental alerts (temperature or humidity)

Machine status reports in industrial systems

Simple home automation notifications

Future extensions could include:

ESP32 port with full SSL/TLS support *(planned)*

Brevo API integration for cloud dashboards *(planned)*

Email reports after OTA updates *(idea)*

---

### **Conclusion**

To wrap up, this project proves that
with a **WIZnet W5500 Ethernet Controller**, even low-memory boards can perform dependable network tasks.
Hardware TCP/IP offload removes the heavy lifting from the MCU,
leaving enough resources to build practical features like email alerts.

It’s a clear example of how WIZnet technology extends what small MCUs can do.

👉 **Call to Action:**
Try building your own email-enabled IoT node with W5500 and EMailSender.
All sources and guides are available on [GitHub – xreef/EMailSender](https://github.com/xreef/EMailSender).

Thank you for reading.

---

Source: https://maker.wiznet.io/Benjamin/projects/arduino-uno-mega-and-ethernet-sending-emails-with-attachments-emailsender-v4-0-0-library/