POP/IMAP mailbox vs. Alias
SUMMARY
A mailbox is where your mail actually sits and waits for you. If you then want to get it and download to your computer that is done with a (POP) configuration. If you want to leave it on the server & read it with your email program &/or webmail that is done with an (IMAP) configuration. (Details including pros & cons below).
An alias is an email address that routes the email to your mailbox.
DISCUSSION
ALIAS VS. MAILBOX
What is the difference between an alias and a mailbox?
Here’s an analogy: A mailbox is like your postal mailbox at your house or your PO Box at the Post Office. You use an email program to retrieve the email for the account, just like you go to the end of the driveway or to the Post office to your mailbox to retrieve your postal mail.
An alias, on the other hand, is like a mail forwarding address which forwards to a mailbox somewhere that you specify. An alias forwards your email to a mailbox as a mail forwarding address forwards your mail from one postal mail address to another (yes, you can have an alias to an alias as long as it winds up somewhere retrievable.
Restated, a mailbox is the final destination of email, whereas an alias forwards or re-routes your email to that final destination.
The reason you would want to use an alias is for your convenience. That could mean to have for professional look or perhaps to note the source of an email inquiry for marketing reasons. If you have on your web site, info@mycoolproduct.com and you get an email to that address you know its origin without setting up an entirly new mailbox on your computer.
An alias is the easiest to setup and integrate into your existing world. If you already have an email account that you check somewhere (a mailbox no doubt), the alias can be configured to send your email to that existing account. Nothing special need be done in your email software.
When creating a mailbox, you must then configure your email program to retrieve the messages, or check your mail at the server with a web mail program, such as the one that comes with your hosting found at http://webmail.yourdomain.com. It often makes sense to have at least one mailbox, whereas you could have dozens of alias.
THREE WAYS TO ACCESS YOUR MAILBOX
WEBMAIL
This is the easiest solution. You just point your browser to
http://yourdomain.com/webmail (this is, of course, for the Crestone Hosting server with Crestone Creations).
and, of course <yourdomain> is replaced with YOUR domain – such as crestonecreations.com 
Once you go to that address (it will re-route you to yourdomain.com:2095) you have a login page where you enter your full email address & email password. You then have 3 choices of webmail viewers. I suggest Roundcube. Horde is more powerful, but a bit more awkward. You can set (at any time) to automatically use one service or another.
The Catch with Webmail:
Since you are storing email on the server you must be mindful of storage space. With large file emails stored on the server you may exceed your account limits and discover that you can no longer send / receive emails. Webmail requires periodic maintenance – leave on the server for as long as needed and then, when no longer needed, remove via delete & empty trash.
POP
This is the easy solution for accessing your mailbox when using an email program on your computer such as Mail.app, Outlook, Thunderbird, etc.. POP is easier to setup, easier to maintain, never a worry about exceeding your account limits on the server. This is the preferred setup choice for those who want a simple solution.
POP stands for Post Office Protocol. It is a protocol that mail programs use to download mail from a POP mail server. The mail server receives your e-mail when YOU are not connected to the Internet. Your mail is stored on the server and once you connect to the server through your e-mail client, the email is then downloaded to your computer. The e-mail client then sends a request to the POP mail server, and your e-mail is transferred from the server to your computer.
Setup in a Nutshell, click here
IMAP
IMAP stands for Internet Message Application Protocol. There. Still have questions? ;) ok, …
To make a long story short, when you setup an account as IMAP you are working directly on the server. Local copies are kept on your computer, but moving, deleting, creating mailboxes, etc. is actually happening on the server at the same time. This is great for managing your email via multiple computers and devices.
The Catch with IMAP:
Since you are storing email on the server you must be mindful of storage space. With large file emails stored on the server you may exceed your account limits and discover that you can no longer send / receive emails. IMAP requires periodic maintenance – leave on the server for as long as needed and then, when no longer needed, remove via delete & empty trash OR move the emails to a folder on a local computer.
Setup in a Nutshell, click here