IT Engineer Toolbox
A collection of utilities for IT professionals and engineers
WHOIS Lookup
Look up domain registration information and ownership details
Results:
DNS/NS Lookup
Query DNS records including A, AAAA, MX, TXT, NS, and more
Results:
SPF, DKIM & DMARC Checker
Validate email authentication records for your domain
Common selectors: default, google, k1, selector1, selector2
SPF Record
DMARC Record
DKIM Record
SPF, DKIM & DMARC Generator
Generate email authentication records for your domain
Space-separated list of IP addresses
Space-separated list (e.g., _spf.google.com for Google Workspace)
Email Header Analyzer
Analyze email headers to trace delivery path, authentication results, and potential issues
In Gmail: Open email → Click "Show original" → Copy all headers
In Outlook: Open email → File → Properties → Copy Internet headers
Summary
Authentication Results
Delivery Path (Received Headers)
All Parsed Headers
IP Address Calculator
Calculate subnet information, network address, broadcast address, and usable IP ranges
Results
Network Information
Address Range
Binary Representation
Class & Type
Let's Encrypt Certificate Generator
Generate free SSL/TLS certificates using Let's Encrypt and Certbot
Certificate Information
Space-separated list for multiple domains
For renewal and security notices
Installation Steps
1. Install Certbot
2. Obtain Certificate
3. Configure Auto-Renewal
4. Web Server Configuration
Certificate File Locations
Important Notes
- Ensure your domain points to your server's IP address
- Port 80 (HTTP) must be accessible for domain validation
- For wildcard certificates, use DNS challenge method
- Certificates are valid for 90 days and auto-renew
- Test renewal with:
sudo certbot renew --dry-run
Quick Reference
Common Certbot Commands
sudo certbot certificates List all certificates sudo certbot renew Manually renew certificates sudo certbot delete Delete a certificate sudo certbot revoke --cert-path /path Revoke a certificate Challenge Methods
- HTTP-01: Default method, requires port 80 access
- DNS-01: For wildcard certs, requires DNS TXT record
- TLS-ALPN-01: Alternative to HTTP, uses port 443