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

Description

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
| Node | Type | Purpose |
|---|---|---|
| Schedule Trigger | Trigger | Run at a specific time each day |
| Get many messages | Gmail (getAll) | Search emails since yesterday with filters |
| Loop Over Items | Split in Batches | Iterate messages one-by-one |
| Get a message | Gmail (get) | Fetch full message payload |
| Get message data | Code | Extract HTML/subject/from/date; normalize sender and date |
| Clean | Code | Reformat date and forward fields to LLM |
| Message a model | OpenAI | Summarize email into JSON topics |
| Merge | Code | Merge topics from all emails |
| Create template | Code | Render a styled HTML email digest |
| Send a message | Gmail (send) | Deliver the digest email |

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.

2) Gmail
Get many messages:
Adjust filters.q to your senders/labels and window:
Example: =(from:[email protected]) OR (from:[email protected] -"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.

3) 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