After switch to vps : php mail not working any more

Since I switched to a VPS email sending thru a php program using mail instruction is not working any more.

I tried the following shell command :

In /etc/postfix/ :
inet_interfaces =,

Do I have to adjust parameters, how and where.

Thank for help

Must I

I replaced
inet_interfaces =,
inet_interfaces = all

and it works again.