Scale up as you grow — whether you're running one virtual machine or ten thousand.

From GPU-powered inference and Kubernetes to managed databases and storage, get everything you need to build, scale, and deploy intelligent applications.

I am having problems with setting up a mail server on my droplet. here are my confusions
When adding an mx record, I am asked to add something like mail.sitename.com, my question is how do I setup this sub-domain or is it set setup automatically?
I have already installed postfix and dovecot but I cant receive any emails sent to the created address during configuration
How do i install roundcube to my droplet, I have seen varying tutorials on this and its getting confusing
I am running Ubuntu 14.04 on my digitalocean.
Thanks.