Here is a (not exaustive) list of online tools to check your server and services. It is provided "as it is" without any agreement between Sentora and the linked website owners and without any garanties.
Let you propose your prefered on-line tools with the "Want to help?" box at bottom of the page.
To check DNS configuration:
To follow DNS propagation after any change:
To check your server access:
To check FTP access:
To check website optimization:
To check email services:
To setup and test SPF record:
To check email sending and spam level
To check htaccess redirections
Multiple testers pages: