So I want to use mail() function in PHP. Does it come with default debian install or do I have to install sendmail or that?

Anyways I tried and I get this.....

/>apt-get install sendmail
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
sendmail: Depends: sendmail-bin but it is not going to be installed
E: Broken packages



mail() function returns 1 meaning it was successful however no email is received.

Run apt-get update before trying to install anything new.

If somehow sendmail doesn't work for you, postfix is just as good and possibly more secure as well.