Monitor SSL certificate expiry with Google Sheets and SMTP email alerts

Description

Who is this for?

DevOps engineers, sysadmins, and website owners who manage multiple domains and need proactive SSL certificate expiration monitoring without manual checks.

What it does

Automatically monitors SSL certificates across multiple domains, tracks expiration status in a Google Sheet dashboard, and sends beautifully formatted HTML email alerts before certificates expire.

✅ No API rate limits — Uses direct OpenSSL commands, so you can scan unlimited domains with zero API costs or restrictions.

How it works

Triggers on schedule (every 3 days at 10AM)
Reads domain list from your Google Sheet
Checks each domain's SSL certificate using OpenSSL commands
Parses expiration dates, issuer info, and calculates days remaining
Updates Google Sheet with current status for all domains
Sends styled email alerts only when certificates are expiring soon

Set up steps

Connect your Google Sheets OAuth2 credentials
Create a Google Sheet with these columns: Domain, Expiry Date, Days Left, Status, Issuer, Last Checked (the workflow matches on the Domain column to update results)
Add your domains to scan in the Domain column
Update the Sheet ID in the Read Domain List from Google Sheets and Update Google Sheet with Results nodes
Connect SMTP credentials in the Send Alert Email via SMTP node
Optionally adjust ALERT_THRESHOLD_DAYS in two nodes: Prepare Domain List and Set Threshold and Parse SSL Results and Identify Expiring Certs (default: 20 days)

Setup time: ~10 minutes