Create Daily Newsletter Digests from Gmail using GPT-4.1-mini

Summary

Every day at a set time, this workflow fetches yesterday’s newsletters from Gmail, summarizes each email into concise topics with an LLM, merges all topics, renders a clean HTML digest, and emails it to your inbox.

What this workflow does

• Triggers on a daily schedule (default 16:00, server time)
• Fetches Gmail messages since yesterday using a custom search query with optional sender filters
• Retrieves and decodes each email’s HTML, subject, sender name, and date
• Prompts an LLM (GPT‑4.1‑mini) to produce a consistent JSON summary of topics per email
• Merges topics from all emails into a single list
• Renders a styled HTML email with enumerated items
• Sends the HTML digest to a specified recipient via Gmail

Apps and credentials

• Gmail OAuth2: Gmail account (read and send)
• OpenAI: OpenAi account

Typical use cases

• Daily/weekly newsletter rollups delivered as one email
• Curated digests from specific media or authors
• Team briefings that are easy to read and forward

How it works (node-by-node)

• Schedule Trigger
  • Fires at the configured hour (default 16:00).
• Get many messages (Gmail → getAll, returnAll: true)
  • Uses a filter like:
    =(from:@.com) OR (from:@.com) OR (from:@.com -"____") after:{{ $now.minus({ days: 1 }).toFormat('yyyy/MM/dd') }}
  • Returns a list of message IDs from the past day.
• Loop Over Items (Split in Batches)
  • Iterates through each message ID.
• Get a message (Gmail → get)
  • Retrieves the full message/payload for the current email.
• Get message data (Code)
  • Extracts HTML from Gmail’s MIME parts.
  • Normalizes the sender to just the display name.
  • Formats the date as DD.MM.YYYY.
  • Passes html, subject, from, date forward.
• Clean (Code)
  • Converts DD.MM.YYYY → MM.DD (for prompt brevity).
  • Passes html, subject, from, date to the LLM.
• Message a model (OpenAI, model: gpt‑4.1‑mini, JSON output)
  • Prompt instructs:
    - Produce JSON: { "topics": [ { "title", "descr", "subject", "from", "date" } ] }
    • Split multi-news blocks into separate topics
      • Combine or ignore specific blocks for particular senders (placeholders ____)
    • Keep subject untranslated; other values in ____ language
      • Injects subject/from/date/html from the current email
• Loop Over Items (continues)
  • Processes all emails for the time window.
• Merge (Code)
  • Flattens the topics arrays from all processed emails into one combined topics list.
• Create template (Code)
  • Builds a complete HTML email:
    - Enumerated items with title, one-line description
    - Original subject and “from — date”
    - Safely escapes HTML and preserves line breaks
    - Inline, email-friendly styles
• Send a message (Gmail → send)
  • Sends the final HTML to your recipient with a custom subject.

Node map

Before you start

• Connect Gmail OAuth2 in n8n (ensure it has both read and send permissions)
• Add your OpenAI API key
• Import the provided workflow JSON into n8n

Setup instructions

1. Schedule

• Schedule Trigger node:
• Set your preferred hour (server time). Default is 16:00.

1. Gmail

• Get many messages:
  • Adjust filters.q to your senders/labels and window:
    - Example: =(from:news@publisher.com) OR (from:briefs@media.com -"promo") after:{{ $now.minus({ days: 1 }).toFormat('yyyy/MM/dd') }}
  • You can use label: or category: to narrow scope.
• Send a message:
  • sendTo = your email
  • subject = your subject line
  • message = set to {{ $json.htmlBody }} (already produced by Create template)
  • The HTML body uses inline styles for broad email client support.

1. OpenAI

• Message a model:
  • Model: gpt‑4.1‑mini (swap to gpt‑4o‑mini or your preferred)
  • Update prompt placeholders:
    - ____ language → your target language
    • ____ sender rules → special cases (combine blocks, ignore sections)

How to use

• The workflow runs daily at the scheduled time, compiling a digest from yesterday’s emails.
• You’ll receive one HTML email with all topics neatly listed.
• Adjust the time window or filters to change what gets included.

Customization ideas

• Time window control:
  • after: {{ $now.minus({ days: X }) }} and/or add before:
• Filter by labels:
  • q = label:Newsletters after:{{ $now.minus({ days: 1 }).toFormat('yyyy/MM/dd') }}
• Language:
  • Set the ____ language in the LLM prompt
• Template:
  • Edit “Create template” to add a header, footer, hero section, logo/branding
  • Include links parsed from HTML (add an HTML parser step in “Get message data”)
• Subject line:
  • Make dynamic, e.g., “Digest for {{ $now.toFormat('dd.MM.yyyy') }}”
• Sender:
  • Use a dedicated Gmail account or alias for deliverability and separation

Limits and notes

• Gmail size limit for outgoing emails is ~25 MB; large digests may need pruning
• LLM usage incurs cost and latency proportional to email size and count
• HTML rendering varies across clients; inline styles are used for compatibility
• Schedule uses the n8n server’s timezone; adjust if your server runs in a different TZ

Privacy and safety

• Emails are sent to OpenAI for summarization—ensure this aligns with your data policies
• Limit the Gmail search scope to only the newsletters you want processed
• Avoid including sensitive emails in the search window

Sample output (email body)

• Title 1
  • One-sentence description
  • Original Subject
  • → Sender — DD.MM.YYYY
• Title 2
  • One-sentence description
  • Original Subject
  • → Sender — DD.MM.YYYY

Tips and troubleshooting

• No emails found? Check filters.q and the time window (after:)
• Model returns empty JSON? Simplify the prompt or try another model
• Odd characters in output? The template escapes HTML and preserves line breaks; verify your input encoding
• Delivery issues? Use a verified sender, set a clear subject, and avoid spammy keywords

Tags

• gmail, openai, llm, newsletters, digest, summarization, email, automation

Changelog

• v1: Initial release with scheduled time window, sender filters, LLM summarization, topic merging, and HTML email template rendering