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Email Newsletter System with SendGrid, Google Sheets & Freemium Rate Limiting
https://n8nworkflows.xyz/workflows/email-newsletter-system-with-sendgrid--google-sheets---freemium-rate-limiting-11759
# Email Newsletter System with SendGrid, Google Sheets & Freemium Rate Limiting
### 1. Workflow Overview
This workflow implements an **Email Newsletter System** integrating **SendGrid**, **Google Sheets**, and a **Freemium Rate Limiting** mechanism. Its primary purpose is to process email newsletter requests received via a webhook, differentiate between free ("demo") and pro users, enforce a daily sending limit for free users, and update user sending statistics in a Google Sheet. It also sends email notifications through SendGrid and alerts the administrator via Telegram.
The workflow is logically divided into the following blocks:
- **1.1 Input Reception and User Mode Check:** Receives newsletter data via webhook and checks if the user is "demo" (free) or "pro".
- **1.2 User Existence Verification:** Reads Google Sheets to check if the user exists and retrieves their sending history.
- **1.3 Rate Limiting Check:** For demo users, verifies if the daily sending limit (5 emails/day) has been reached.
- **1.4 User Data Update and Email Sending:** Updates Google Sheets with new usage counts and sends the email via SendGrid.
- **1.5 Response and Notifications:** Sends success or limit-exceeded responses to the requester and sends Telegram notifications to the administrator.
---
### 2. Block-by-Block Analysis
#### 2.1 Input Reception and User Mode Check
- **Overview:**
Receives incoming newsletter requests from a web form, parses the payload, and routes processing based on user mode ("demo" or "pro").
- **Nodes Involved:**
- Webhook1
- Check Mode1
- Send Email (Pro)
- Success Response (Pro)1
- **Node Details:**
- **Webhook1**
- Type: Webhook
- Role: Entry point; listens for HTTP POST requests at path `236f9261-dd76-47e7-b09a-2667a0f315bf`.
- Config: Receives JSON body containing email data including mode, from, to, subject, html content.
- Inputs: None
- Outputs: To Check Mode1
- Edge Cases: Invalid/malformed payload, unauthorized requests (no auth configured here).
- Version: 1
- **Check Mode1**
- Type: If
- Role: Determines if the user is "demo" (free) or "pro" based on `mode` field in payload.
- Config: String condition checking if `mode` contains "demo".
- Inputs: From Webhook1
- Outputs: True branch (demo) -> Google Sheets Read; False branch (pro) -> Send Email (Pro)
- Edge Cases: Missing or unexpected mode value may misroute flow.
- Version: 1
- **Send Email (Pro)**
- Type: SendGrid
- Role: Sends the email for pro users without limit checks.
- Config: Uses `from`, `to`, `subject`, `html` from webhook data; sender email hardcoded; content type HTML.
- Inputs: False branch from Check Mode1
- Outputs: Success Response (Pro)1
- Credentials: SendGrid API required.
- Edge Cases: SendGrid API failures, invalid emails, quota exceeded.
- Version: 1
- **Success Response (Pro)1**
- Type: Respond to Webhook
- Role: Sends JSON success response to pro users after email is sent.
- Config: Response body confirms success with mode "pro".
- Inputs: From Send Email (Pro) node
- Outputs: None (ends flow)
- Edge Cases: Response failures if webhook is closed.
- Version: 1
---
#### 2.2 User Existence Verification
- **Overview:**
For demo users, reads Google Sheet to find existing user data, then uses code logic to determine if user exists or not.
- **Nodes Involved:**
- Google Sheets Read
- Check User Exists2 (Code)
- Check User Exists1 (If)
- **Node Details:**
- **Google Sheets Read**
- Type: Google Sheets
- Role: Reads rows from "Email_Tracker" sheet filtering by `Email` matching webhook `from` email.
- Config: Filter `Email` column equals webhook `body.from`. Sheet ID and GID specified.
- Inputs: True branch from Check Mode1
- Outputs: To Check User Exists2
- Credentials: Google Sheets OAuth2 required.
- Edge Cases: API limits, missing sheet, no matching rows.
- Version: 4.5
- **Check User Exists2**
- Type: Code
- Role: Processes Google Sheet results to determine if user exists; marks existence flag.
- Config: Checks for non-empty Email rows; sets `exists` boolean accordingly.
- Inputs: From Google Sheets Read
- Outputs: To Check User Exists1
- Edge Cases: Empty result sets, case sensitivity in email.
- Version: 2
- **Check User Exists1**
- Type: If
- Role: Branches flow based on user existence flag.
- Config: Boolean condition on `exists` field.
- Inputs: From Check User Exists2
- Outputs: True (user exists) -> Check Limit Logic; False (new user) -> Create New User1
- Edge Cases: Improper boolean evaluation, missing flag.
- Version: 2
---
#### 2.3 Rate Limiting Check
- **Overview:**
Checks if the demo user has sent fewer than 5 emails today; resets daily counter if needed.
- **Nodes Involved:**
- Check Limit Logic (Code)
- Can Send?1 (If)
- Limit Reached Response1
- Update User Count1
- Create New User1
- **Node Details:**
- **Check Limit Logic**
- Type: Code
- Role: Implements logic to check if daily email count is below 5, resets count on new day, returns updated counters and flags.
- Config: Uses JavaScript Date to compare today's date with last send date; increments or resets send count accordingly; flags canSend boolean.
- Inputs: True branch from Check User Exists1 (user exists)
- Outputs: To Can Send?1
- Edge Cases: Date format mismatches, missing fields, parsing errors.
- Version: 2
- **Can Send?1**
- Type: If
- Role: Branches flow depending on canSend boolean from previous node.
- Config: Boolean condition on `$json.canSend === true`
- Inputs: From Check Limit Logic
- Outputs: True -> Update User Count1; False -> Limit Reached Response1
- Edge Cases: Missing or malformed canSend field.
- Version: 2
- **Limit Reached Response1**
- Type: Respond to Webhook
- Role: Sends HTTP 429 error response indicating daily free email limit reached.
- Config: Response includes error message, limit info, and current count.
- Inputs: From Can Send?1 (false branch)
- Outputs: None (ends flow)
- Edge Cases: Response delivery failures.
- Version: 1
- **Update User Count1**
- Type: Google Sheets
- Role: Updates existing user row with incremented daily and total send counts, and last send date.
- Config: Update by matching `Email` column; increments `Total_Sent` by 1; updates `Send_Count` and `Last_Send_Date`.
- Inputs: From Can Send?1 (true branch)
- Outputs: To Send Email (Demo)1 and Telegram Notification1
- Credentials: Google Sheets OAuth2 required.
- Edge Cases: Update conflicts, concurrency issues, API errors.
- Version: 4
- **Create New User1**
- Type: Google Sheets
- Role: Appends new user row for a previously unseen demo user with initial counts set to 1.
- Config: Creates row with email, `Send_Count = 1`, `Total_Sent = 1`, and current date as `Last_Send_Date`.
- Inputs: False branch from Check User Exists1 (new user)
- Outputs: To Telegram Notification1 and Send Email (Demo)1
- Credentials: Google Sheets OAuth2 required.
- Edge Cases: Append errors, duplicate entries.
- Version: 4
---
#### 2.4 User Data Update and Email Sending
- **Overview:**
Sends the demo user email using SendGrid, then sends success response and Telegram notification.
- **Nodes Involved:**
- Send Email (Demo)1
- Success Response (Demo)1
- Telegram Notification1
- **Node Details:**
- **Send Email (Demo)1**
- Type: SendGrid
- Role: Sends the email for demo users after passing the limit checks.
- Config: Uses email parameters from webhook; sender name is the `from` field in webhook; content type HTML.
- Inputs: From Update User Count1 or Create New User1
- Outputs: To Success Response (Demo)1
- Credentials: SendGrid API required.
- Edge Cases: API errors, invalid email data.
- Version: 1
- **Success Response (Demo)1**
- Type: Respond to Webhook
- Role: Sends JSON success response confirming email sent for demo user, includes remaining emails count for the day.
- Config: Response JSON includes success flag, message, mode "demo", and remaining emails (5 - newCount).
- Inputs: From Send Email (Demo)1
- Outputs: None (ends flow)
- Edge Cases: Response failures.
- Version: 1
- **Telegram Notification1**
- Type: Telegram
- Role: Sends notification message to administrator Telegram chat about demo email sent and remaining quota.
- Config: Custom text including sender, recipient, and remaining emails; uses configured chat ID.
- Inputs: From Update User Count1 and Create New User1 (parallel)
- Outputs: None
- Credentials: Telegram API credentials required.
- Edge Cases: Telegram API errors, invalid chat ID.
- Version: 1.2
---
### 3. Summary Table
| Node Name | Node Type | Functional Role | Input Node(s) | Output Node(s) | Sticky Note |
|-----------------------|--------------------|-----------------------------------------------|------------------------|-------------------------------------------|----------------------------------------------------------------------------------------------------|
| Webhook1 | Webhook | Receives newsletter data via HTTP POST | None | Check Mode1 | ## 1. Receive data from newsletter page, validate if free or pro user. Process free user and send pro user's message |
| Check Mode1 | If | Checks if user mode is demo or pro | Webhook1 | Google Sheets Read (demo), Send Email (Pro) (pro) | |
| Google Sheets Read | Google Sheets | Reads user data from sheet based on email | Check Mode1 (demo) | Check User Exists2 | |
| Check User Exists2 | Code | Determines if user exists in Google Sheet | Google Sheets Read | Check User Exists1 | |
| Check User Exists1 | If | Branches on existence of user | Check User Exists2 | Check Limit Logic (exists), Create New User1 (not exists) | ## 2. Check if user has used up the 5 free email limit daily. Send error message if exceeded |
| Check Limit Logic | Code | Checks and updates daily send count | Check User Exists1 | Can Send?1 | |
| Can Send?1 | If | Branches on if user can send email or not | Check Limit Logic | Update User Count1 (can send), Limit Reached Response1 (limit reached) | |
| Update User Count1 | Google Sheets | Updates user's send counts in Google Sheet | Can Send?1 (true) | Send Email (Demo)1, Telegram Notification1 | ## 3. Update database, send email and notification to self |
| Create New User1 | Google Sheets | Creates new user entry in Google Sheet | Check User Exists1 (false) | Telegram Notification1, Send Email (Demo)1 | |
| Send Email (Pro) | SendGrid | Sends email for pro users | Check Mode1 (pro) | Success Response (Pro)1 | |
| Success Response (Pro)1| Respond to Webhook | Sends success JSON response to pro user | Send Email (Pro) | None | |
| Send Email (Demo)1 | SendGrid | Sends email for demo users | Update User Count1/Create New User1 | Success Response (Demo)1 | |
| Success Response (Demo)1| Respond to Webhook| Sends success JSON response to demo user | Send Email (Demo)1 | None | |
| Limit Reached Response1| Respond to Webhook | Sends 429 error response when limit reached | Can Send?1 (false) | None | |
| Telegram Notification1 | Telegram | Sends Telegram admin notification | Update User Count1, Create New User1 | None | |
| Sticky Note | Sticky Note | Notes for block 2 (limit check) | None | None | ## 2. Check if user has used up the 5 free email limit daily. Send error message if exceeded |
| Sticky Note1 | Sticky Note | Notes for block 3 (update & notification) | None | None | ## 3. Update database, send email and notification to self |
| Sticky Note2 | Sticky Note | Notes for block 1 (input & validation) | None | None | ## 1. Receive data from newsletter page, validate if free or pro user. Process free user and send pro user's message |
| Sticky Note3 | Sticky Note | Full workflow overview and setup instructions | None | None | ## Email Newsletter Builder with Rate Limiting and User Tracking [Get the Email Newsletter Builder Webform](https://drive.google.com/file/d/1ZipYXImNi8JbwnekzphqHoFKf5Qbhu6g/view?usp=sharing) [Get the Google Sheet Template](https://docs.google.com/spreadsheets/d/1JvsOzkCaJzJN8-x1hldFA-H6iPc0A9MH-mVYBCEWtJw/edit?usp=sharing) |
---
### 4. Reproducing the Workflow from Scratch
1. **Create Webhook Node:**
- Name: `Webhook1`
- Type: Webhook (HTTP POST)
- Path: `236f9261-dd76-47e7-b09a-2667a0f315bf`
- Response Mode: Response Node
- No authentication configured here (consider adding for production)
2. **Create If Node to Check Mode:**
- Name: `Check Mode1`
- Type: If
- Condition: String contains
- Value1: `{{$json.body.mode}}`
- Value2: `demo`
- Connect `Webhook1` main output to `Check Mode1` input.
3. **Create Google Sheets Read Node:**
- Name: `Google Sheets Read`
- Type: Google Sheets (Read)
- Document ID: Your Google Sheet ID (e.g., `1OLIz-oxje6O-RjhVv0NXyNOrgd3hALTYnBKjo27sj9Q`)
- Sheet Name: `Sheet1` (gid=0)
- Filters: Filter by column `Email` equals `={{ $json.body.from }}`
- Credentials: Configure Google Sheets OAuth2 API
- Connect `Check Mode1` TRUE output (demo) to this node.
4. **Create Code Node to Check User Exists:**
- Name: `Check User Exists2`
- Type: Code
- Code:
```javascript
const email = $node["Webhook1"].json.body.from.toLowerCase();
const realRows = items.filter(item => item.json.Email && item.json.Email.trim() !== '');
if (realRows.length > 0) {
return realRows.map(item => ({ json: {...item.json, email, exists: true} }));
}
return [{ json: { email, exists: false, matches: 0 } }];
```
- Connect `Google Sheets Read` to this node.
5. **Create If Node to Branch on User Existence:**
- Name: `Check User Exists1`
- Type: If
- Condition: Boolean
- Left Value: `={{ $json.exists }}`
- Operation: Equals `true`
- Connect `Check User Exists2` output to this node.
6. **Create Code Node for Limit Check:**
- Name: `Check Limit Logic`
- Type: Code
- Code:
```javascript
const today = new Date().toISOString().split('T')[0];
const userDate = $input.item.json.Last_Send_Date;
const sendCount = parseInt($input.item.json.Send_Count) || 0;
let newCount1 = sendCount;
let newCount = $input.item.json.Total_Sent;
let canSend = false;
if (userDate === today) {
if (sendCount < 5) {
canSend = true;
newCount1 = sendCount + 1;
}
} else {
canSend = true;
newCount1 = 1;
}
return {
canSend,
Total_Sent: newCount,
Send_Count: newCount1,
Email: $input.item.json.Email,
rowNumber: $input.item.json.row_number,
Last_Send_Date: today
};
```
- Connect TRUE output from `Check User Exists1` to this node.
7. **Create If Node for Can Send?:**
- Name: `Can Send?1`
- Type: If
- Condition: Boolean equals `true` on `{{$json.canSend}}`
- Connect `Check Limit Logic` output to this node.
8. **Create Google Sheets Update Node:**
- Name: `Update User Count1`
- Type: Google Sheets (Update)
- Document ID and Sheet Name same as before
- Matching Column: `Email`
- Columns to update:
- Email: `{{$json.Email}}`
- Send_Count: `{{$json.Send_Count}}`
- Total_Sent: `{{$json.Total_Sent + 1}}`
- Last_Send_Date: `{{$json.Last_Send_Date}}`
- row_number: 0 (read-only, ignored in update)
- Connect TRUE output of `Can Send?1` to this node.
9. **Create Google Sheets Append Node for New Users:**
- Name: `Create New User1`
- Type: Google Sheets (Append)
- Columns:
- Email: `{{$node["Webhook1"].item.json.body.from}}`
- Send_Count: 1
- Total_Sent: 1
- Last_Send_Date: `{{$now.format("yyyy-MM-dd")}}`
- Connect FALSE output of `Check User Exists1` here.
10. **Create SendGrid Node to Send Demo Email:**
- Name: `Send Email (Demo)1`
- Type: SendGrid
- Parameters:
- Subject: `{{$node["Webhook1"].item.json.body.subject}}`
- To Email: `{{$node["Webhook1"].item.json.body.to}}`
- From Name: `{{$node["Webhook1"].item.json.body.from}}`
- From Email: Your verified sender email address
- Content Type: `text/html`
- Content Value: `{{$node["Webhook1"].item.json.body.html}}`
- Credentials: SendGrid API credentials required
- Connect outputs of `Update User Count1` and `Create New User1` to this node.
11. **Create Success Response Node for Demo:**
- Name: `Success Response (Demo)1`
- Type: Respond to Webhook
- Response Mode: JSON
- Response Body:
```json
{
"success": true,
"message": "Email sent successfully!",
"mode": "demo",
"remaining": 5 - {{$json.Send_Count}}
}
```
- Connect output of `Send Email (Demo)1` here.
12. **Create Limit Reached Response Node:**
- Name: `Limit Reached Response1`
- Type: Respond to Webhook
- HTTP Response Code: 429
- Response Mode: JSON
- Response Body:
```json
{
"success": false,
"error": "Daily limit reached (5 emails/day)",
"message": "You've reached your daily limit. Upgrade to Pro for unlimited sends!",
"current_count": {{$json.Send_Count}}
}
```
- Connect FALSE output of `Can Send?1` here.
13. **Create Telegram Notification Node:**
- Name: `Telegram Notification1`
- Type: Telegram
- Chat ID: Your Telegram chat ID
- Text:
```
📧 Demo email sent from: {{$node["Webhook1"].item.json.body.from}}
✉️ To: {{$node["Webhook1"].item.json.body.to}}
📊 Remaining today: {{5 - $json.Send_Count}}
```
- Credentials: Telegram Bot API credentials required
- Connect outputs of `Update User Count1` and `Create New User1` here.
14. **Connect Pro User Branch:**
- Connect FALSE output of `Check Mode1` to `Send Email (Pro)`.
- Configure `Send Email (Pro)` similarly to demo email node but with fixed `From Name` "Pro User".
- Connect `Send Email (Pro)` output to `Success Response (Pro)1` node.
15. **Test the workflow end-to-end** ensuring correct data flows and credentials are valid.
---
### 5. General Notes & Resources
| Note Content | Context or Link |
|------------------------------------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------|
| Email Newsletter Builder with Rate Limiting and User Tracking. Setup instructions and webform & sheet templates included. | See Sticky Note3 content inside the workflow JSON. |
| Register on SendGrid and link the API key to SendGrid nodes for email sending. | https://login.sendgrid.com/login/ |
| Create a Telegram bot and get chat ID for notification node credentials. | https://web.telegram.org/a/ |
| Download the Email Newsletter Builder Webform template. | https://drive.google.com/file/d/1ZipYXImNi8JbwnekzphqHoFKf5Qbhu6g/view?usp=sharing |
| Download the Google Sheet Template for tracking user email sends. | https://docs.google.com/spreadsheets/d/1JvsOzkCaJzJN8-x1hldFA-H6iPc0A9MH-mVYBCEWtJw/edit?usp=sharing |
---
**Disclaimer:** The provided text originates exclusively from an automated n8n workflow and adheres strictly to content policies. It contains no illegal or offensive elements. All data handled is legal and public.