Why, right? With so many free services why getting your own email server? Well I cannot give you a definitive answer but I can give you some good reasons by wich you should use your own mail server. The first is privacy. Today pretty much of our data is on the cloud. Funny name, cloud. But what exactly do we mean by I've got everything in the cloud. Well basically it means that we are technically lazy and decide to third party every service we use to private companies. Is this a problem? Well not at first. That should not be a problem to have my data on servers that are monitored 24/7 and that has several dozens of engineers ready to overcome some tech problem it may arise. It is also very nice not to care about the resilience of the service because typically these are very reliable too. But we are missing something. And that something is privacy. The moment your data enter in the google or facebook server in some of theirs datacenters the data stops being yours. At that moment you have zero garanties that those companies will not mess with your data. Well for most of the people and for the most of the time this was not a problem at all. However recent news show how easy is for governments to get access to our data and how private companies leverage profits on our allegedly private data. Do you want an example? Well have you ever noticed that your facebook account have advertisements that are somehow related with your last amazon search, and/or purchased items? How does this happens. Well some of them map the email that you register in one platform with the same email on the other platform and by doing this they correlate your facebook identity with you amazon account. This is more and more a common practice. By having your own mail server you have virtually infinite email accounts. You don't need to try mails like John.firstname.lastname@example.org because there is no John on your mail server. To avoid the cross sharing of identities you can create a bunch of accounts each for one platform you use. For example
By doing this you are enforcing different identities and avoiding the problem of cross sharing of emails. You will reduce the amount of "artificial inteligence" between these platforms but, on the other hand, you'll enforce some degree of separation between those. You should remember that if you send a mail to a friend that has his mail account on google that your mail will be on google servers. If you, neverthless, want to ensure your privacy you could use PGP and use cryptography to ensure that the data is not readable in the google servers.