Exim4 how to and tips

Exim4 setup, issues, removal, status.

Removal :

Remove Exim4.

Setup :

Setup Exim4.

Status :

Check if Exim4 is working.
Where to find the email sent.
Check if Exim4 is running.

Issues :

Socket bind() to port 25 for address failed.
Paniclog has non-zero size, mail system might be broken.
Could not instantiate mail function on WordPress.
Setting the unprivileged uid to 0 is not recommended.