Name:MxToolBox (Free)
URL:https://mxtoolbox.com/NetworkTools.aspx/
Description:All in one multi-purpose network tool
Utility:This free tool can – 

• Check IP or host 
• Lookup DNS for IP address
• Perform Domain Lookup
• Perform DNS Reverse Lookup
• Test Mail Server SMTP
• Check DNS Servers
• Lookup DNS for IPv6
• Lookup DNS for Location
• Find Location from IP
• Find a Domain’s Health Status
• Find Port Status
• Perform Website Query – HTTP and HTTPS
• Ping
• Traceroute
• Analyse Header of Emails
• Extract Email from any Text
• Check URL Reputation
• Provide Email deliverability Report
• Check DNS Propagation
• Generate Password 
• Monitor email end to end 
• Monitor an entire sub-net and much more