Understanding Email Services: A crash course in email jargon

July 23rd, 2013

You thought email was a simple concept, but you are at once confronted with a plethora of acronyms and jargon like POP, IMAP, WebMail, Aliases, Forwards, SMTP, IMAP, POP, Quota, SPAM, TLS, SSL, Archival, and more! This article describes the ins and outs of email, explains these terms, and helps you figure out what services and features you need from your personal or business email service provider.

Every email provider supplies you with three fundamental services:

  • A way to send email
  • A way to receive email
  • A way to store received email, at least temporarily

The difference between email providers, and their cost, comes down to the support they offer, versatility, security, and extent of each of these services. In the next sections, we discuss each of these concepts in detail and consider many of the possible and/or desired features that could be included with them. First, we will define a few concepts central to email — the types of programs (a.k.a “email clients”) used for email.

Email Clients.

Email clients are computer programs that run on your computer, laptop, tablet, or smartphone which enable you to perform actions such as composing and sending email messages, retrieving your new email messages, and looking at your old email messages. Examples of popular email clients include: Mozilla Thunderbird, Microsoft Outlook, Mac Mail, Entourage, and iPhone Mail (read more about these).

Email clients are characterized by being installed on a computer of device in that you have or have access to, and requiring you to configure them with details of your email provider so that they can connect to your provider to send and receive your email.


WebMail (a.k.a. “web-based email” or “browser-based email”) is like an email client in that it allows you to compose and send email messages, view new and old email messages, and perform other email activities. However, unlike an email client, WebMail is a web browser-based program that runs in part in your computer’s web browser and in part on your email provider’s web servers and which is accessible via any computer connected to the Internet which has a compatible web browser, such as a recent version of Internet Explorer, Firefox, Opera, Safari, Chrome, etc.

WebMail is notably different from an email client in that you do not have to configure it or install any special software to use it, beyond a good web browser.  You simply “login”, and it works.  However, WebMail often permits customization through preferences and settings that you can manipulate to make it work and behave to your specifications.

Sending Email: SMTP

Any email message that you send is passed along from your computer through any number of intermediate email servers to the server on which the recipient of your message receives his or her email. All of these email servers talk to each other via a language (a protocol) called SMTP, which stands for Simple Mail Transport Protocol.  Thus, your outgoing email server (i.e. the server through which you send email messages) is also known as your SMTP server.

Every email provider has one or more SMTP servers for your use. Some providers allow you to connect to these servers directly so that you can send email using your Email Client; other providers do not permit you to connect to their SMTP servers directly, requiring you to send all email via their WebMail applications (which use the SMTP servers behind the scenes).

Why would an email service provider not want clients to connect directly to its SMTP servers? Using an Email Client, you may be able to easily send lots of email messages, whereas with WebMail it is difficult to send many messages in a short period of time.  Allowing you to send lots of email messages in a short time exposes your email provider to the risk that you may 1. load down his servers with excessive amounts of email, and 2. send SPAM.  For this reason, some email providers also have strict limits on sending through their SMTP servers and other providers have special services for customers needing to send large quantities of email.

If your email provider does provide you with access to its SMTP servers, it may or may not support “SMTP Relaying”. Support for “SMTP Relaying” means that your provider allows you to use its SMTP server to send email to people whose email is not managed by your provider. For example, if you are using the SMTP servers of LuxSci to send email to bob@luxsci.net, this would not require SMTP Relaying because LuxSci’s servers handle Bob’s email, and thus they HAVE to let you connect to them to send him email (or else Bob would unfortunately never receive any email).  However, if you are using LuxSci’s servers to send email to bob@hotmail.com, this would require SMTP Relaying because LuxSci does not manage the email for addresses at hotmail.com.

What’s wrong with SMTP Relaying? Nothing, as long as your email provider restricts who can use its servers for sending email. If they don’t, then anyone could send email through their servers to anyone else, making these servers ideal tools for hackers desiring to send SPAM (such a wide open server is called an “Open Relay” and is almost always a guaranteed to be on email blacklists). For this reason, most email providers require you to Authenticate yourself when using their SMTP servers for sending email. This often means that you need to send your correct username and password to their server before it will allow you to send your email. This process is commonly called SMTP Authentication. Some email providers go a step further and also provide you with Secure SMTP. Secure SMTP (along with other secure services described below) encrypts the communication between your computer and the server using TLS or SSL such that no one can eavesdrop and detect your username, password, or message contents – the communication channel is secure.

What is right for you? If you wish to use an email client for sending and reading your email, your email provider must provide you with “SMTP Relaying” services. If you are very security-conscious, you should ask if they support Secure SMTP.  LuxSci provides both SMTP Relaying (with authentication), Secure SMTP, and additional email encryption options.

Receiving Email: POP, IMAP, WebMail

If someone sends you an email message, how do you obtain it and read it? There are three basic ways to do this which differ in usefulness depending on your needs.

WebMail. WebMail applications have several advantages:

  1. Read It Anywhere – They allow you to read (and send) email from any computer that is connected to the Internet and that has a modern web browser.
  2. No Special Software – Beyond a modern web browser, which comes with most computers, no special software is required to use WebMail, and no time needs to be spent configuring software.
  3. Can Be Secure – Most WebMail applications run over a secure connection between your browser and the email provider’s servers (an SSL – Secure Socket Layer – connection) so that all of your email messages, passwords and other data cannot be eavesdropped upon. Many WebMail services do not provide this, however.
  4. Backed-up & Safe – Your email service provider is responsible for backing up your email messages. Your email is stored on your service providers servers, so if your personal computer crashes, none of this email is affected!

The disadvantages of WebMail include:

  1. Internet Required – You cannot view any of your email unless you are connected to the Internet. The speed by which you can manage your email is related to your Internet connection speed — it can be slow or fast!
  2. Disk Space – Since your email messages are stored on your email provider’s servers, they take up his disk space. Your email provider may limit the amount of disk space you can use, or charge you a premium for additional disk space. If you exceed your allotted disk space, you could be charged a fine or your services could be suspended! Most free email services are very strict about disabling your account if you exceed your quota. These days, disk space is not much of an issue unless you are an email hoarder.
  3. Features – Your provider’s WebMail program may not provide you with as many features as you would have if you used an Email Client for reading your email. The features provided by different providers’ WebMail clients vary greatly — make sure yours provides those features that you need! I.e., some features include: sending attachments, viewing attachments online, viewing messages written in particular languages, address books, personalities, spell checking, read receipts, SPAM filtering, autoresponders, email aliases, drag and drop, uploading and downloading many files at once, etc., etc.

A good email provider will supply you with WebMail services and one or both of IMAP or POP (see below) and possibly also ActiveSync for use with Email Clients and mobile devices.

IMAP is a protocol, i.e. a language used by an Email Client program to talk to your email provider’s servers. It stands for Internet Mail Access Protocol. IMAP is one of the two most popular protocols that can be used by Email Clients to allow you to access your email messages. IMAP allows you to keep some or all of your email messages stored on your service provider’s servers, thus sharing many of the pros and cons of WebMail. Your service provider may offer Secure IMAP (a.k.a. IMAPS) which makes sure that the data sent back and forth between your Email Client and the server cannot be eavesdropped upon. Secure IMAP connections are encrypted via the same technology that encrypts secure WebMail — SSL (or TLS).  IMAP does not generally permit sending of email messages, you would still use SMTP for that.

Use of IMAP provides the following advantages:

  1. Read It Anywhere – Read email from any computer that is connected to the Internet and which has an Email Client supporting IMAP installed.
  2. Backed up & Safe – You email service provider is responsible for backing up your email messages. Your email is stored on your service providers servers, so if your personal computer crashes, none of this email is affected!
  3. Features – You can use any modern Email Client which provides you with all of the email management features that you require.
  4. Download – Most Email Clients allow you to download some or all of your email messages from the server to your local computer for viewing while you are not connected to the Internet, or for archiving without taking up disk space on your provider’s servers.
  5. View only Headers – Your IMAP client can download and display only the headers of the messages in your email folders, thus requiring little bandwidth until you need to actually view the body of a message.
  6. Server Side – many operations such as sorting messages, searching, and moving messages between folders can be done by the server without requiring you to download the messages involved, thus requiring little bandwidth and making them very fast.
  7. WebMail Compatible – All of the email that you keep on the server (even if it is sorted into multiple folders) can be viewed by either WebMail or an Email Client using IMAP. This is great for people who travel.

The disadvantages of IMAP include:

  1. Internet Required – You cannot view any of your email unless you are connected to the Internet (unless the email client supports an Offline mode for viewing messages, and you have enabled this). The speed by which you can view your email is related to your Internet connection speed — it can be slow or fast!
  2. Disk Space – Since your email messages are stored on your email provider’s servers, they take up his disk space. Your email provider may limit the amount of disk space you can use. If you exceed the allotted disk space, you could be charged a fine or your services could be suspended!
  3. Software – You must obtain, install and configure your Email Client software on each computer that will be used for checking your email via IMAP.

POP is also a protocol. It stands for Post Office Protocol. Sometimes you will see it written as POP3 which implies Version 3 of the Post Office Protocol. POP is the other of the two most popular protocols that can be used by Email Clients to access your email messages. POP enables you to automatically download your messages from your Inbox on the email server to your local computer (and usually to then remove them from the Inbox on the server). This is intrinsically different from IMAP and WebMail, where the email always stays on the email server. Your service provider may also offer Secure POP (a.k.a. POPS) which makes sure that the data sent back and forth between your Email Client and the servers cannot be eavesdropped upon.

Use of POP provides the following advantages:

  1. Disk Space – Because POP usually downloads all messages to your local computer and automatically deletes them from your email provider’s server, you minimize the amount of disk space that you use on the servers, possibly lowering the cost of your account.
  2. Speed – Once your email messages are downloaded on your local computer, you can read them very easily and quickly, even if your computer is no longer connected to the Internet.

The disadvantages of POP include:

  1. Not Anywhere – Since your email is downloaded to your local computer, you cannot view this email from any other machine. If you travel or go home from work, you lose access to your downloaded email (unless you copy it to a disk and take it with you!)
  2. Software Required – You must obtain, install and configure your Email Client software on each computer that will be used for checking your email via POP.
  3. You Manage Backups – As your email is on your local computer, you take all responsibility for ensuring that you have backups of your email messages in the event that something goes wrong with your computer.
  4. Multiple devices – People commonly access their email using a number of devices — a work computer, a home computer, a laptop, a smartphone, a tablet, etc.  If you use POP, it is likely that email will be downloaded to one of these devices and then no longer be visible on the other ones.  Even if you try to configure POP to “keep email on the server” … this is slow and inefficient and it is likely that at some point you will make a mistake and all that email will be downloaded to one of your devices anyway; this happens all the time.

Email providers like to offer POP email boxes because you download all the email from their servers, minimizing the impact of your email usage on their servers. They dislike providing IMAP services, as IMAP users can leave gigabytes of email on their servers and exert much more of a computational load on their servers. Email providers offering IMAP services are usually more expensive than those that do not for exactly these reasons — and these are good reasons!

ActiveSync (or “Exchange ActiveSync”) is a protocol developed by Microsoft for synchronizing mobile devices with its Exchange email and collaboration system.  However, it is really just a protocol like POP and IMAP and it enables mobile devices to securely read email, send email, synchronize email folders, contacts, calendars, task lists, and get updates in real time (through “push” notifications from your service provider’s servers to your mobile devices).  As of this writing, Exchange ActiveSync is available natively on most mobile devices and also in Outlook 2013 for Windows.  ActivesSync is generally better than POP, IMAP, and SMTP for mobile use as it is designed for the mobile environment, supports fast “push” updates, and can be easier on your mobile device batteries.  For email, it behaves much like using SMTP plus IMAP; however, it has the great advantage of also synchronizing your contacts, calendars, ans tasks, so you can always access them “on the go”.  LuxSci’s ActiveSync option is called MobileSync.


Compare Features

WebMail IMAP/ActiveSync POP
Access Email From Anywhere? Yes Yes No
Large Server Disk Usage Yes, Unless you use POP as well Yes Minimal
Dependence on Internet Connectivity Strong Very Strong Moderate
Special Software Needed? No Yes Yes
Data Backup Responsibility Service Provider’s Service Provider’s Yours
Security Depends on Provider Depends on Provider Depends on Provider

What is right for you? If you wish to use an email client for sending and reading your email, your email provider must provide you with POP and/or IMAP services. If you wish to access your email from multiple computers (i.e. when traveling), then WebMail and/or IMAP services are essential. WebMail is always a plus as it generally works in conjunction with IMAP and can be used even with POP to view new messages that have not yet been downloaded by your Email Client. If you are looking for the least expensive solution, use WebMail in conjunction with POP. IMAP adds a lot of flexibility and power, but also requires that you purchase more disk space with your email provider and have a reliable and speedy Internet connection. If you are very security-conscious, you should ask for Secure versions of any of the services that you need.

Important Email Concepts / Definitions

Security & Privacy

Email is an inherently insecure communication medium. Learn why this is so and what you can do about it in this article “The Case For Email Security“.


Sending a message, especially an advertisement, to more than a few recipients, can by itself be considered spamming unless the individuals have specifically requested to be added to a mailing list on that topic. This includes commercial advertisements and informational messages sent to recipients via electronic mail. Email is a person-to-person medium, not a broadcast medium.

There are many laws that affect the sending of Spam and Unsolicited Commercial Email (UCE), such as the Can-Spam Act.  Most email providers and Internet service providers have strict policies against the use of their services for such purposes. Sending of unsolicited email is very bad Net-Etiquette.

What is the problem with SPAM?  Unlike postal mail, email is virtually cost free to the sender, so advertisers have no problem sending unlimited quantities of email in the hope that some small percentage will result in sales, or responses. The result is that an ever growing proportion of email is SPAM — current projections indicate that in several years, more than 90% of email will be SPAM, greatly diminishing the use of email as an effective means of communication.

Sending SPAM, unsolicited commercial email (UCE) or any unsolicited email to multiple people is considered an abuse of your email provider’s services and may subject your account to immediate cancellation.

What about that list of 100,000 opt-in email addresses I purchased? Any opt-in email list is going to have people on it that will complain if you send them email, and the burden of proof is upon you, the sender, not on them! So if you sent 100,000 emails and %0.1 of the people complain, you just got 100 complaints! That’s enough to get your account terminated with almost any email provider! The only safe way to use opt-in email lists is to create the lists yourself via your own web site – not by buying it from anyone, no matter how “reputable”, and certainly NOT by scanning or spidering the Internet and grabbing people’s email addresses from their web pages!

Also, it is generally accepted that “opt in” means “opted in specifically to receive your content”.  Thus, it is not possible to buy a list of people who have opted into your mailings, as they would have no specific information about your mailings when they purportedly opted in.

To help with the proliferation of Internet SPAM, most email providers offer SPAM Filtering software. This is software built into your provider’s servers that can detect a large proportion of the SPAM being sent to your email address(es). Detected SPAM emails can then be deleted, stored in alternate email folders, bounced back to the sender, or simply marked as potential SPAM.  Be careful with such software as, incorrectly configured, it can result in the loss of important non-SPAM email (i.e. false positives) .. e.g. disappearing email.

Email Aliases and Email Boxes/Users

Both email aliases and email boxes (i.e. users) are email addresses, like bob@luxsci.net, to which email can be sent.  An email box is the address of an actual user on the email provider’s server and usually corresponds to the address that the user uses to login to the email services.  E.g. if bob@luxsci.net is an email box, then bob@luxsci.net is an actual username on the luxsci.net servers and “bob@luxsci.net” can be used as a login to the IMAP, POP, WebMail, and possibly other services.  An alias, however, is not an actual user, but rather merely a rule that indicates what to do with email addressed to a particular email address.

For example, let’s say that fred@luxsci.net is an email alias. We then also have to say where email to fred@luxsci.net should go. One possibility is that we configure the email alias such that email for fred@luxsci.net is automatically forwarded to bob@luxsci.net. In this case any email sent to eitherbob@luxsci.net or fred@luxsci.net gets deposited in bob@luxsci.net‘s email box.

Thus, email aliases allow one, to receive email sent to lots of different email addresses in the same email box or to forward email sent to specific addresses to multiple recipients as a distribution list.

One special kind of email alias is called a Catch-All Alias. If you have a catch-all alias for your domain then all email addressed to addresses in the domain that don’t correspond to email boxes or other email aliases will be delivered to the recipient(s) of the catch-all alias. These are often used to make sure that you get any email sent to any address at your domain (e.g. to catch email to misspelled recipient addresses). However, using a catch-all alias subjects you to the receipt of more SPAM — SPAM sent to any address is caught by the catch-all alias!  For this reason, we recommend against the use of catch-all aliases.

Email Personalities.

Your Email Personality is applied to the email messages that you send. It consists of who the message is “From” and to whom replies to the message should be sent to. Most simply, your email personality consists of your Name and Email Address; however, you may wish to use “multiple personalities” — one for your “Sales” department email, one for your “Support” email, one for your “Personal” email, one for your “Academic” email, etc. Each personality might use a different email address and name.

Some WebMail interfaces allow you to configure multiple personalities and choose the personality of your outgoing email message when you are composing the message. This is very convenient, especially if you would like to manage all of your email in one place (e.g. you wear “multiple hats” in your business, or have different email addresses for different purposes). Note that any WebMail program that allows you to specify arbitrary personalities will include information in your email messages indicating from whom they were actually sent, allowing them to be tracked back to you – this protects your email provider from possible use of this service for illegal purposes. So, be careful to use only personalities that you rightfully own or to which you are authorized.

Personalities may also allow you to configure “Signature” content to be added to the end of your email messages.  This is often used to provide your contact information, advertisements, and/or a legal disclaimer on your messages.


Also known as an “out-of-office response”, an “away message”, or a “vacation message”, an autoresponder automatically sends an email message back to the senders of messages that you receive. You can usually customize these automatic responses to have any fixed subject and body that you desire. Autoresponders are often used to inform senders that you are, for some reason, not checking your email for a time, that your email address is changing, that the email arrived in your email box, or of other important information.

Email Archival.

Due to government regulation and business needs, email archival is becoming more and more common.  With email archival, copies of all messages sent and received by all users are made and saved in a location where you can access them, search them, and download them later.  Email archival services usually ensure that the storage is immutable, meaning that the messages cannot be deleted or edited, and is redundant, so that the messages are stored in multiple location for safety.

Email archival is recommended for any business or organization that uses email for important communications as it provides an infallible backup and insurance policy that you can always go back and find that critical email message when needed.

Private Labeling.

Some email providers support skinning, branding, or private labeling their Web-based interfaces so that you can make their interface look like it belongs to your company.  This is good for preserving your brand identity, when you have customers accessing that web portal, or for providing a more corporate atmosphere, when your staff is using the interface.  “Co-branding” is like private labeling, except that the provider’s name is not hidden.  I.e. you could have co-branded WebMail that is “Your Company Mail powered by Your Provider”.  Fully private labeled services do not mention the provider’s name anywhere, not even in the addresses used to access the service.


If you have your own email servers but require that your outbound email be channeled through some other company for filtering, encryption, archival, or some other reason, then you may configure your existing email server so that it sends all email though that company’s email server instead of trying to deliver that email directly to its recipients.  This is known as “smarthosting” and the company’s email server that is receiving all of your email is known as the “smart host”.

Shared vs Dedicated or Virtual Machine

Shared email accounts are generally inexpensive as you share a server at your email provider with other unrelated customers.  However, if you have a larger account (in terms of people, or usage requirements) you may find that the cost of a shared account does not scale well … and a “dedicated server” or “virtual server” will provide a better price point.  Or, you may find that a dedicated server provides additional security and privacy that you find important. Dedicated solutions put your entire account on a  server that is not shared with anyone else and the pricing is usually much more liberal — you are paying more for the server than for small increments in services or users.  See: