I am currently running my on debian wheezy with php5 installed. I was trying use the mail() function, and I realised that I will require a MTA/exim installed before it will be possible because the default installation does not come with any.
I was looking at a solution at: https://wiki.debian.org/GmailAndExim4
However, it says that This setting is for a typical desktop PC which has no resolvable host name.
Are there any good references for the settings I can use for a hosting server?