I know how to perform basic through to fairly advanced tasks in on-premises and cloud-based Exchange systems but I still sometimes get confused when trying to use the terminology.

Here's what I think I know:

  1. User account. An Active Directory / Windows Azure object which contains information about the user and is used for authentication and access to systems.
    • Username. A unique identifier of a user account.
  2. Domain. Used to manage a group of objects. When used for email the domain's DNS records (MX, usually, but others can be used too for additional functionality, such as AutoDiscover, spam-checking, etc) must be configured to point at the mail server. The name of a domain can be anything when used internally but when used publically on the Internet it has to be registered via a domain name registrar and is formatted as %secondleveldomainname%.%topleveldomain% but can also be %subdomainname%.%secondleveldomainname%.%topleveldomain%.
    • User Principal Name. An extended unique identifier of a user account which explicitly targets a specific domain. The format is %username%@%domain% (eggs@ample.com), which is commonly but erroneously referred to as "email address format"
  3. Mailbox. An Exchange object that stores all mail, contact, calendar, task, note, other email-related data (inbox rules, etc), delegate access information, etc. Can exist without a user account and an attached user account can be changed.
    • SMTP alias. A "pathway" to a mailbox. Can literally be anything but mail will only be delivered internally if the domain is not registered. Mailboxes can have many SMTP aliases and all receive mail into the mailbox but one is the primary and is used to send mail (although, why you can't send from multiple I've never understood).
    • Display Name. A non-unique and easily-understood identifier of a mailbox, usually used to inform recipients who the sender is.
  4. Email account. User account + mailbox.

(I know that these terms are not specific to Microsoft products and some are used for more than one thing but I'm concentrating on these. I've also probably forgotten to add loads of other things)

Also, I'm never quite sure how to reference a specific email account. Currently, I use the following:

  • "@domain" for an email account with multiple "username aliases" (?).
  • "sendaddress@" for an email account with multiple "domain aliases" (?).
  • "Display Name" for an email account with multiple "username aliases" and "domain aliases" (?) or owners.
  • "Person's account" for an email account where the aforementioned identifiers cannot clearly convey the ownership.

The problem with these is that they aren't "static" (that is, they can all be changed) and there's too much confusion with SMTP aliases when using referencing with UPNs, so the information may be obsolete in the future.


Can anyone clarify whether this is correct and offer any corrections and/or advice for using the terminology better?


Username. A unique identifier of a user account.

Username isn't an attribute of a user account. Unique fields are SAMAccountName, User Principal Name, Name, and Distinguished Name (among others).

The name of a domain can be anything when used internally

It shouldn't be anything. I've blogged about this fairly extensively: http://www.mdmarra.com/2012/11/why-you-shouldnt-use-local-in-your.html

User Principal Name [....] which explicitly targets a specific domain

Not sure what you mean by "target" but you can define arbitrary UPN suffixes, they aren't required to match up to a DNS domain that you own/control (though they probably should).

Now as for your actual questions: I have no idea what you're asking. Please re-read your post and edit it to be a little more clear, so that I can come back and edit this into something useful to you :)

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  • Interesting blog! So, everything else is fairly accurate? Sorry, I can't think of how to phrase my question better. – mythofechelon Apr 9 '14 at 22:50

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