Some useful tools to help diagnose any issues..

Your IP

Check your IP address

Ping a host

Ping a host name or IP address

Domain DNS lookup

Look up and test dns entries

Whois

Whois information

FTP to a host

Check an FTP connection

Test HTTP server

Checks an HTTP connection

Email checker

Check if an email address can accept mail.

Mail server black list

Check if the address of your mail server is blocked.

Test SMTP

Tests an SMTP connection

Time checker

Check the current time!.

GEO location checker

Check if your device is GEO location enabled.