Gmail Auto-Reply Workflow with OpenAI GPT-5-mini (n8n)

Instant Gmail auto-acknowledgements powered by OpenAI (n8n)

This n8n workflow automatically monitors your Gmail Inbox for new unread messages, filters out auto-generated or sensitive emails, uses OpenAI (gpt-5-mini) to draft a brief personalized acknowledgement, then replies in Gmail and marks the email as read—saving you time while keeping your responses warm and human.

What this workflow does

• Checks Gmail every minute for new unread messages addressed to you (and excludes threads where the subject starts with “Re:”).
• Extracts sender details (sender name and email address) and screens out likely bot/noreply, team mailboxes, auto-generated/list messages, and messages that resemble password, fraud, or security alerts.
• Avoids duplicate replies by searching your Gmail Sent mail for messages to the same sender within the last 3 days.
• If the sender passes screening and hasn’t been replied to recently, the workflow sends the incoming email content and sender name to OpenAI gpt-5-mini to generate a short plain-text acknowledgement.
• Replies in Gmail with the generated text and then marks the incoming message as read.

Use cases

• SaaS operators who need immediate acknowledgment for inbound support or sales emails without manual triage.
• Automation engineers who want a safe, rules-based Gmail auto-reply system with OpenAI drafting.
• Busy founders who want confirmation to senders while they review messages later.

Technical details

• Gmail Trigger: monitors Inbox for new unread emails using Gmail search filters (including -subject:"Re:" and a configurable newer_than window).
• if / code logic: performs screening (bot/noreply, list-like, and security/fraud-like patterns) and reply eligibility checks.
• Gmail (search sent mail): checks Sent messages to the same sender within the last 3 days.
• OpenAI via n8n LangChain nodes: n8nn8n-nodes-langchain lm (chat OpenAI) using gpt-5-mini to draft the acknowledgement.