As it was mentioned by Anonymous generaly is a very bad idea to use mail server on a broadband connection. Google/hotmail/yahoo will reject emails straight away from these ip blocks mo matter what.
Of course the article says what hardware to buy first. Well do not buy anything, you will need a fix public ip from a proper isp, so therefore you need a virtual private server.
Mine is at the moment with OVH which cost me £1.99/month. Fix public ip, 1gb ram, 10gb hdd.
At Hetzner you could get this same server for about 6 quid.
So all in all if you buy any hardware and try to use your broadband for mail/web server, then you will spend 10x more on hardware than you should and also about the same on electric bill to run your small pc.
All small boxes eats up about 20-30w. Also if you try to use any proper MX relay for your broadband, that will also cost about the same amount monthly than a vps server.
Make a calcultation, spend days weeks on the whole lot and you will still end up buying a vps server.
I tried it didnt work, so dont waste your energy on it.
By the way if you have a vps with centos/debian then it takes to fully get configured about 1 day.
On mine i got postfix/dovecot/spamassassin + roundcubemail for webmail.
If you want ssl certificate them get it from ssls.com cost 7 quid for 1 year.