Who runs SSLMonitor?
SSLMonitor is published by the team behind Forward Email, a small team that runs an open source email service. The script exists because certificate expiry alerts are a common reason to send email from a server, and Forward Email can deliver those alerts through its API or SMTP.
Forward Email is open source (github.com/forwardemail/forwardemail.net). Its free plan works without an account: you set MX and TXT records on your domain and mail is forwarded. Paid plans add outbound SMTP and the email API that SSLMonitor uses. Forward Email supports IMAP, POP3, SMTP, CalDAV and CardDAV, and you can self-host it with Docker. Its founder was one of the first employees at DuckDuckGo.
What is on this site?
The SSLMonitor home page explains what the script does and how to start. The rest of the site covers one task per page:
- Install guide: requirements, every setting, cron, log rotation and troubleshooting, plus the full script.
- Email alerts: when a report is sent, what it contains and the two ways to deliver it.
- Command line checks: tested
opensslcommands to check any certificate by hand. - Certificate lifetimes: the CA/Browser Forum validity schedule and the alert thresholds that fit it.
- FAQ: short answers about cost, scope and limits.
Every page is also available as plain Markdown by adding .md to its address (for example /install.md), and /llms.txt lists them for language models.
Source code
The script, this website and its build script are on GitHub at forwardemail/sslmonitor.com. Every page has an edit link in the footer. Issues and pull requests are welcome.
Contact
- Bugs, questions and suggestions: open a GitHub issue.
- Security problems: email security@forwardemail.net as described in the Forward Email security policy, and do not post them in public issues. The same contact is in this site's
/.well-known/security.txtfile. - Forward Email accounts and email delivery: Forward Email help.
Privacy
This site sets no cookies and loads no analytics, trackers, fonts or scripts from other sites, so your browser only talks to sslmonitor.com. The pages contain no JavaScript at all.
Requests to sslmonitor.com pass through Cloudflare, which runs as a CDN and proxy in front of GitHub Pages and processes the IP address of each visitor (Cloudflare privacy policy). GitHub Pages hosts the files, and GitHub logs the IP address of visitors for security purposes; see the GitHub Privacy Statement for details.
The script itself sends data only where you configure it: it connects to the domains in your list and, when an alert is due, sends the report to the Forward Email API or your local sendmail.
Editorial policy
The Forward Email team writes and reviews every page. Facts about certificate rules on this site link to their primary sources: the CA/Browser Forum Baseline Requirements, Let's Encrypt and the Certbot documentation. Descriptions of the script come from its source code. Commands on the command line page were tested with OpenSSL 3.0 on Linux. Their sample output uses example names and dates. If something is wrong or out of date, please open an issue and the page will be corrected.