Email aliases and mailboxes are not interchangeable. Using a mailbox simply to forward email could be severely limiting your email flexibility.
Whether you're setting up a website or an ISP email account, it's important to know the functional differences between email aliases and mailboxes. They are not interchangeable.
First, it would help to note the difference between a POP (Post Office Protocol) account and an SMTP (Simple Mail Transfer Protocol) account. Although the ability to send and receive email comes with most email accounts, receiving email is normally accomplished through a POP (input) account, while sending email is an 'SMTP' (output) feature.
Mailboxes and email aliases deal with the POP (receiving) aspect of your email. A POP account is essentially a mailbox. As the term mailbox implies, it's like a real-life mail box, a place to receive your mail (a major difference being that email travels at the speed of light while regular mail sometimes never sees the light of day.) Once in your mailbox, email just sits there until you 'retrieve' it. (Some services allow mailboxes to be forwarded, but then you'd need another mailbox to receive the email in.)
This is where setting up your 'email client' (Outlook, Netscape email, Eudora, etc.) comes in. By setting up the mail-server, ID and password parameters, you tell the program where to retrieve your email from. Many email clients even give you the option to 'leave email on server after retrieval.' This means that you can retrieve your email (with the 'leave email ...' option on) on your laptop, when you're away from home, for example, then later, when you get home, retrieve the same email messages on your desktop (where you might want to keep a more permanent record of your email).
Once you retrieve email with the 'leave email...' option off (perhaps on your desktop, in the above example), the same email messages are no longer available for retrieval; they have been deleted from the server.
Email aliases are a different animal. Let's say you have a website mysite.com and you've set up a mailbox 'mybox;' so your email address is now email@example.com. Now you decide that your cousin, who works for you, also needs an email address. So you set up an email ALIAS firstname.lastname@example.org. (If the only reason you hired him is to make your aunt in Wisconsin happy, you might give him an email address like email@example.com.)
This email alias, firstname.lastname@example.org, MUST be forwarded to a mailbox, or another alias which eventually goes to a mailbox. This is because aliases do not have a 'box' of their own for email to accumulate in; they are simply forwarding tools.
As a result, if email@example.com were forwarded to firstname.lastname@example.org, when you retrieve your email for email@example.com you will automatically also get the email for firstname.lastname@example.org. Using this approach, you can have many aliases forwarded to one mailbox.
Why, then, you might ask, would anyone ever need more than one mailbox? Good question. (Why didn't I think of that?)
One reason might be, let's say your aunt from Wisconsin comes to work for you and you want to give her the email address email@example.com. (If the only reason you're hiring her is because your cousin can't live without her, you might want to give her the email address firstname.lastname@example.org.) If you make her email address an alias (as opposed to a mailbox), then every time you retrieve your email from email@example.com, you'll also get her email, which was sent to firstname.lastname@example.org. What's worse, if you give her access to the mailbox so she can retrieve her own email, she'll also see your email. Technically, there's nothing wrong with this. But from a family relations standpoint, this may lead to 'technical difficulties' of another kind.
So, you make email@example.com a mailbox, not an alias. (The menu options for setting up aliases and mailboxes can vary from one service to another, so I won't get into that.) Now she can retrieve her email directly from firstname.lastname@example.org and you can still retrieve your email from email@example.com, and neither one of you would see nor interfere with the other one's email. This would probably be the best solution; because the last thing you want is to find out that your aunt is not really your aunt, your cousin is not really your cousin, and that you were adopted, and you're not even you. This can't be good for business.
Email accounts given to you by an ISP (like Earthlink, Verizon, etc.) are usually much simpler in construction and less flexible. In a simple setup, you might get one mailbox with several aliases that automatically get forwarded to the mailbox. If this is good enough for you, there's no need to mess with your website's email features. One serious downside to this is if you change ISPs, you'll have to give people your new email addresses. While if you use domain-based email addresses and then change your web hosting company, presumably your domain name will go with you and your old email addresses will remain valid.
The only question remaining now is, if you change your ISP, you change your hosting company, and you change your business location, do your aunt and cousin come with you? Even tech support can't answer this question.
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