Automate Email Invoice Saving to Nextcloud with n8n

Opening Problem Statement

Meet Sarah, an accountant at a growing company that receives dozens of invoice emails daily. Her job involves downloading each invoice attachment from a dedicated ‘Invoices’ email folder, renaming the files for consistency, and uploading them to her team’s Nextcloud storage organized by date and sender. This process eats up at least two hours every day, multiplies human errors like misplaced or wrongly named files, and delays accounting workflows significantly. Sarah’s frustration is relatable to many who deal with repetitive email attachment management tasks that are critical yet time-consuming.

What This Automation Does

This specific n8n workflow automates Sarah’s entire invoice attachment handling process seamlessly and effectively. When activated, it:

• Connects to an IMAP email account and reads all emails in the “Invoices” folder.
• Extracts each attachment from all emails, even multiple attachments per email.
• Sanitizes and standardizes attachment filenames by removing invalid characters and truncating long names.
• Organizes files by sender name and email date in Nextcloud, creating date-stamped folders automatically.
• Uploads the cleaned attachment files to the correct Nextcloud folder based on their email metadata.
• Reduces manual effort drastically, saving Sarah approximately 10+ hours weekly and virtually eliminating file mismanagement errors.

Prerequisites ⚙️

• 📧 IMAP Email account configured to access the “Invoices” mailbox.
• 📁 Nextcloud account with access configured for file uploads.
• 🔑 Credentials set up in n8n: IMAP email credentials and Nextcloud API credentials.
• ⏱️ An active n8n instance (cloud or self-hosted via platforms like Hostinger).

Step-by-Step Guide

Step 1: Set Up IMAP Email Node to Read Invoice Emails

In your n8n editor, add an IMAP Email node by clicking “+” → Search for IMAP Email → Select it.

Configure it by selecting your email credentials and setting the parameters:

• Mailbox: Set to Invoices to target your invoice emails folder.
• Format: Choose resolved to get attachments and parsed metadata.
• Options > customEmailConfig: Use the value ['ALL'] to fetch all emails.

Once configured, you should see the node ready to fetch emails from the specified mailbox on execution.

Common mistake: Forgetting to select the correct mailbox will result in fetching no invoices.

Step 2: Add a Function Node to Process and Sanitize Attachments

Add a Function node named Map each attachment.

This node’s functionCode takes each email’s attachments, sanitizes filenames (removes unwanted characters and truncates long names), and formats data for Nextcloud:

const _ = require('lodash')

const sanitize = str => _.chain(str)
  .replace(/[^A-Za-z0-9&.-]/g, '-') // sanitise via whitelist of characters
  .replace(/-(?=-)/g, '') // remove repeated dashes
  .trim('-') // trim any leading/trailing dashes
  .truncate({
    length: 60,
    omission: '-'
  })
  .value()

const result = _.flatMap(items.map(item => {
  return _.values(item.binary).map(file => {
    const filename_parts = file.fileName.split('.')
    const ext = _.slice(filename_parts, filename_parts.length-1)
    const filename_main = _.join(_.dropRight(filename_parts), '.')
    file.fileName = sanitize(filename_main) + '.' + ext
    return {
      json: {
        from: sanitize(item.json.from.value[0].name),
        date: sanitize(new Date(item.json.date).toISOString().split("T")[0])
      }, 
      binary: { file }
    }
  })
}))

return result

You should see each attachment separately mapped and cleaned ready for upload.

Common mistake: Make sure your emails contain attachments; empty emails will cause no output.

Step 3: Configure Nextcloud Node to Upload Files

Add a Nextcloud node and connect it from the Map each attachment node.

Set its parameters:

• Path: Use an expression to organize files inside folders named by the email date and sender: =Documents/Invoices/{{$json["date"]}}_{{$json["from"]}}_{{$binary.file.fileName}}
• Binary Data Upload: Set to true.
• Binary Property Name: Set to file.

Upon execution, the Nextcloud node uploads each sanitized attachment file into its dedicated folder automatically.

Common mistake: Incorrect path expressions can cause files to be misplaced or errors.

Customizations ✏️

• Change Folder Structure: Modify the Path expression in the Nextcloud node to include client names or project codes if available.
• Attachment Type Filtering: Use an additional Function or IF node after the IMAP node to filter attachments by filetype, e.g., only PDFs.
• Add Notification: Integrate an Email or Slack node to notify you when new invoices are uploaded.

Troubleshooting 🔧

Problem: “No attachments found in the email”

Cause: Email messages are empty or do not contain attachments accessible by the IMAP node.

Solution: Check your email mailbox for emails with attachments and validate IMAP permissions.

Problem: “Nextcloud upload failed”

Cause: Invalid authentication or incorrect file path in the Nextcloud node.

Solution: Verify your Nextcloud credentials and ensure your path expression in the node is correct.

Pre-Production Checklist ✅

• Test IMAP connection and fetch one or two emails with attachments successfully.
• Validate Function node outputs sanitized filenames and correct JSON metadata.
• Test Nextcloud node uploads files in correct paths as expected.
• Review your folder structure and naming conventions to avoid conflicts.

Deployment Guide

Activate the workflow by toggling it ON in n8n once configured and tested.

Schedule the execution or trigger manually as needed.

Monitor execution logs in n8n to ensure files are processed and uploaded without errors.

Conclusion

By following this detailed guide, you have automated the tedious and error-prone task of processing email invoices and filing them into Nextcloud. This saves hours weekly and minimizes risks of misfiling important documents. Next steps could involve adding automated invoice data extraction into spreadsheets, invoice payment reminders, or integration with accounting software for end-to-end automation of your finance ops. Keep exploring n8n’s nodes to further ease your workload!