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A Glossary of Email Terms

Account Aggregation

This is our term for collecting email from various different accounts and putting them all together, in one mailbox.
Email can be forwarded directly to your Exchange account's mailbox or email can be collected from other POP3 accounts and placed there.
This includes webmail accounts such as Hotmail and Yahoo where these accounts allow it.
If necessary the "aggregated" email can then all be forwarded-on to a final destination mailbox.
It's obviously a good thing if you only have to look in one place for all your emails.

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ActiveSync

ActiveSync is a Microsoft program which runs on both a mobile device, such as a PDA or SmartPhone, and a PC to allow:-

A mobile device often comes with a cradle for it to sit in which connects, via a USB cable, to a PC although ActiveSync can also operate over a Bluetooth or WiFi connection.
There are 3rd party ActiveSync clients for smartphones that don't use the Windows Mobile operating system

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Bayesian Filtering

Bayesian analysis was invented by the English mathematician the Reverend Thomas Bayes - 1702 to 1761 - and is a method of determining probability based on past events.
It is used in our spam filtering system to rate the probability of an email being spam.
This rating is used, in conjunction which other spam indicators, to make the decision for every email: spam or not spam
Initially, like the Reverend himself, a Bayesian filter knows nothing at all about spam and just guesses but, by telling it each time it makes a mistake, it soon develops its own set of analysis rules and becomes an expert in picking out spam.
Analysing every new email and noting when it's made a mistake, it continues to refine its rules, sometimes discarding older rules, so that it keeps up with the ever-changing nature of spam.
Those nonsense sentences you sometimes see in spam emails are put there to try to confuse  Bayesian filters.

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Black-List

A list of email addresses, email domains or IP addresses known to originate large amounts of spam.
Incoming emails from black-list entries are either refused, automatically classified as spam or given a strong spam score where scores from multiple spam classification methods are totalled to determine if an email is spam.

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DKIM

DomainKeys Identified Mail is an enhanced version of the DomainKeys initiative to fight spam.
It is a merging of DomainKeys and Identified Internet Mail and works in a very similar way to DomainKeys.

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DomainKeys

This is a way of being absolutely sure which mail-server a particular email has originated from. This is important as the originating address of most spam and virus emails has been forged.
DomainKeys uses a combination of digital certificates and a new type of DNS record to identify a mail-server.
A digital certificate has 2 parts: the public key and the private key.
The public key is made available to anyone who wants it and the private key is kept securely inside a company.
If a private key encrypts a message then only the public key can decrypt it and vice versa.
The new type of DNS record is the mail-server's public key and the mail-server "signs" every email it sends using its private key.
With DomainKeys the contents of an email message are not encrypted (there'd be no point as anyone could get the public key to decrypt it) but an encrypted section, called the signature, is added to each email and, if a receiving mail-server can successfully decrypt this with the sending mail-server's public key then the email must have originated from that server.
This system doesn't have such a problem with forwarding emails as has the similar
Sender Policy Framework anti-spam initiative but there is a the same lack of widespread support, at the moment, for the new type of DNS record required to make it work.
Won't the mail-servers that send spam just start using the DomainKeys system?
If they do they will positively identify themselves allowing these mail-servers to be quickly black-listed or even their owners to be prosecuted.
Arrowmail currently signs all outgoing emails using the DomainKeys system but doesn't use the lack of a DomainKeys signature on an incoming email as an indicator that it may be spam.

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Email Domain

The non-personal part of an email address to the right of the @ sign.
The email domain of john.smith@companymail.com is companymail.com
When a mail-server is delivering email to another mail-server across the Internet it only looks at the email domain part of the email address.
Only when the email has arrived at the destination mail-server is the personal part of the email address important.
Here it's used to determine which local mailbox the email should be stored in.
Every email domain requires a DNS MX record to be set which then allows other
mail-servers on the Internet to discover which mail-servers have been nominated to receive emails for that domain.

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False Positive

A genuine email that an anti-spam system has wrongly classified as spam and which has therefore not been delivered to its intended recipient but has either been deleted or moved to a Spam folder for a human to review.
Like death by "friendly fire", a small number of False Positives are an inevitable consequence in the war against spam.
At Arrowmail we consider minimising False Positives as the most important goal of our
anti-spam system.

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Firewall

The term comes from the motor industry where it means the physical barrier between the passenger and engine compartments in a car, used to protect passengers in case of an engine fire.
In computing, a firewall is a filtering device placed at various interfaces around a network to protect the computers on one side of the interface from undesirable network traffic thought likely to be present on the other side.
A secondary purpose is to prevent users accessing proscribed resources and services on the Internet.
The most common place to find a firewall is where a private network connects to the Internet.
A firewall analyses the network traffic that arrives at either of it's interfaces to see if it matches rules that an administrator has set.
A positive match can cause the traffic to be allowed to pass through, be blocked or sometimes pass through in a modified form (such as when performing NAT routing).
No match means the traffic is blocked.
Simple firewalls permit all traffic originating from the trusted internal network to pass while all traffic originating from the Internet is blocked.
Today no network is trusted and there are plenty of examples of an internal PC spreading viruses to other internal PCs.
Individual PCs on an internal network should therefore be running a firewall program for their protection and to contain the effects on any virus or trojan that may have infected them and be trying to spread itself to other PCs and/or send out passwords and creditcard details.
A well setup firewall should not allow any traffic to pass through "by default".
Every type of traffic - originating from either side - that is allowed to pass through should match a rule that is as specific as possible in regard to who can send what to where and when. For instance, if your users want to use MSN messenger there should be a rule that allows it.
Another one of those endless debates is whether you should use a hardware or a software firewall. In reality all firewalls are software programs running on computers.
A "hardware" firewall is a computer whose only purpose is to run the firewall program and the hardware, software and operating system have been optimised for this purpose while a "software" firewall runs on a general purpose computer such as a Windows PC which also performs many other unrelated tasks.
Quick Advice Use a software firewall on a PC and a hardware firewall to connect your network to the Internet.
The Best Firewalls
For individual PCs: Comodo (Windows XP Service Pack 2's built in firewall is OK)
For connecting private networks to the Internet:-
Hardware: Cisco PIX, Netgear's £70 Broadband routers are a good second.
Software: Microsoft ISA 2006 or Kerio WinRoute Firewall.

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Grey-Listing

An anti-spam technique where a receiving mail-server always refuses to accept email for a set time period, such as 15 minutes, after an unknown mail-server tries to send mail to it for the first time.
If the sending mail-server comes back after 15 minutes the email is then accepted and the server added to the receiving mail-server's list of friends.
The theory is that mail-servers sending out millions of spam emails will not bother to retry after the initial failure.

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Ham

The opposite of spam: genuine email.
The term ham is often used to describe the samples of genuine emails used to help a
Bayesian filter more accurately determine what is and isn't spam.

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IMAP - Internet Message Access Protocol version 4

This email protocol was developed to overcome the disadvantages of POP3, namely that downloaded emails are only stored on one PC's hard drive making them vulnerable to being lost if the PC fails or is stolen and, if you check your email on 2 PCs, say at home and at work, email downloaded onto one PC is not accessible from the other.
With IMAP, a master copy of your email is stored on a central well-protected and backed-up mail-server.
This means you see the same set of email folders on any PC you check email on and you don't have to worry about backing up your email folders locally.
A local cached copy of your email folders is stored on each local PC to permit off-line access to email and this local copy is synchronised with the master copy on the server at regular intervals.
IMAP has been around for well over 10 years and is still a useful protocol, especially for checking your Spam Folder for false positives by just examining the headers of an email without not having to completely download every message.
However IMAP is not as popular as Webmail and companies tend to prefer more modern high-end systems, such as Outlook Anywhere, that also synchronise centrally stored copies of your address book, calendar, To Do list and even standard files such as Word documents.
IMAP also handles deleting emails in a strange way.

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IMAPS - Secure IMAP

See SMTPS for a discussion of secure email protocols.

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Mail-Server

A software program that sends, receives and processes emails for users of one or more email domains.
Users connect to their mail-server to send and receive email.
A mail-server also connects with other mail-servers across the Internet to send and receive emails between the local network and other email domains.

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Mailing List

A feature of many mail-servers which provides the best way to send the same email to many recipients.
When an email is sent to the address of the mailing list, the server prepares and sends an individual, personally addressed copy of this email to every member of the mailing list - which can usually be up to 100 separate emails.
Each member receives what appears to be a personally addressed email from the sender, and, more importantly with today's concerns over privacy, the emails definitely do not contain the email addresses of other members of the mailing list.

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OST File

This is the file that Outlook uses, when operating in cached mode with an Exchange server, to store a full local copy of a user's email and other related data where the master copy is held on the Exchange server.
This offline copy allows a user to continue to work with Outlook if the connection to Exchange is broken. When this connection is restored, any changes that have happened to the OST file will be sent back to Exchange and any changes that have happened to Exchange's master copy, such as new emails arriving, will be sent to the OST file so these 2 data stores are back in sync.
If you use Outlook with an Exchange server on more than one computer, there will be an OST file on each one which is like having several backups of your Outlook data.
If you lose connection with Exchange permanently, due to an unrecoverable server crash or you change email providers, the information in the OST file will stay on your PC indefinitely allowing you to either move it to a local PST file or to a new Exchange server.

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Outlook Anywhere

This is the new name for RPC-over-Http or Remote Procedure Call over HyperText Transfer Protocol.
RPC is how Microsoft Outlook and Microsoft Exchange Server communicate when both the PC and server are on the same network inside the same company.
When people are working away from the office with their laptops they ideally want to carry on using Outlook just as they do when in the office.
While RPC can in theory operate over the Internet, no network administrator will, in practice, allow it to pass through their firewall.
RPC can also operate through a VPN over the Internet but when you're travelling around you can never be sure that any particular firewall you connect through has been setup to allow VPN pass-through connections - most VPN systems are technically complicated and firewall unfriendly.
The only thing you can be pretty sure of with an unknown firewall is that it will permit web browsing on TCP Port 80 for http:// webpages and TCP Port 443 for https:// webpages.
Microsoft, therefore, developed a protocol which makes RPC data appear as web browsing traffic.
"RPC data is encapsulated inside an HTTP datagram" is the official description.
In fact to keep this RPC data strongly encrypted as it traverses the Internet, HTTPS encapsulation is used almost exclusively so the correct term is RPC-over-HTTPS however both terms are used to mean the same thing.
Microsoft have now, thankfully, renamed this access method and call it Outlook Anywhere.
Outlook Anywhere is the preferred way of accessing an Exchange server from home or when travelling with your laptop and able to get an Internet connection, but Outlook Web Access (OWA), which also operates over TCP Port 443, is a good-to-have standby for times when you can only get Internet access by using someone else's PC.

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Outlook Mobile Access - OMA

OMA is the simplest possible webmail system for accessing your Exchange mailbox using a web browser.
It is text-only and designed to be used on a PDA or Smartphone.
If you have Direct Push on your mobile device then you may still find OMA useful to
change your password or view the contents of mail folders not marked for synchronisation by ActiveSync.
Microsoft has dropped OMA completely from Exchange 2007 - apparently no one was using it.

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Outlook Web Access - OWA

OWA is Microsoft's name for the webmail system that comes with Exchange Server.
It's a very good simulation of the Outlook desktop program and is the standard by which other webmail systems are judged.

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PDA - Personal Digital Assistant

This is a generic name for a small hand-held computer, usually with a large touch-screen but still small enough to fit into a shirt pocket.
While nowhere near as flexible or powerful as a standard laptop, PDAs are very good at certain tasks such as checking email and satellite navigation.
A modern PDA now has a built-in mobile SIM card to enable it to connect to the Internet from almost anywhere using 3G or GPRS as well as to function as a mobile phone.
There's still a long way to go to make PDAs really useful because:-

Smartphones are very similar to PDAs but are smaller, more of a phone and less of a computer and don't usually come with a touchscreen.

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Phishing

Phishing is the attempt to acquire sensitive information, such as credit card details, or on-line banking logon information, by subterfuge in order to steal money from the individual targeted.
A phishing email usually pretends to be from a genuine on-line company and offers some plausible reason why you need to take some action which will reveal your personal details.
A bogus website has often been setup to capture your information which is a replica of the genuine website.
If you receive a phishing email from a company with which you have an existing relationship, it's very easy to be tricked.
The best defence against phishing is to consider all such communications as fraudulent and if you are worried about the consequences of ignoring the instructions given in the phishing email, then telephone the company concerned to see if the email was genuine.
Most companies now know not to use an email to ask its customers to perform the type of task requested in phishing emails, thus making the likelihood very small of such an email being genuine.
Phishing can also be carried out using phone calls, texts, faxes, letters or even face-to-face.

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POP3 - Post Office Protocol version 3

This is the most common method used to receive emails on a PC by downloading them from a mailbox on a mail-server into the Inbox of an email program.
SMTP is a sender-initiated email transfer method which requires recipients to be on-line all the time, ready to accept email.
POP3 is a recipient-initiated email transfer method where the recipient only needs to be on-line when wanting to collect their email.
The server POP3 mailbox, where new mail can usually wait indefinitely for the client to come and collect it, is the interface between these 2 protocols.
The advantages of POP3 are that it's simple and efficient, making it the best method to use over slow Internet connections and, once downloaded, your emails and attachments are available on your PC even when it's not connected to the Internet.
The disadvantages are that downloaded email messages only exist on the hard drive of the one PC that downloaded them.
This makes them vulnerable to loss if the hard drive fails or the computer is stolen and also not accessible from other PCs you may also use to download email to.

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POP3S or SPOP - Secure POP3

This is the encrypted version of standard plain-text POP3.
See SMTPS for a discussion of secure email protocols.

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PST File

This is the name of the file that Outlook, the email and personal organiser program from Microsoft, uses to store all your Email, Contact, Calendar, Tasks and Notes data plus other related data such email accounts and mailbox rules.

The default name and location of this file is:-

c:\Documents and Settings\<username>\Local Data\Application Data\Microsoft\Outlook\Outlook.pst

In versions of Outlook prior to Outlook 2003, a PST file had a size limit of 2gb.
The default limit is now 20gb with a theoretical maximum size is of 33 terabytes.
PST stands for Personal Storage Table but is more commonly called Personal Folders File.
Having all your Outlook data in one file is convenient but, unless you keep regular backups, you run the risk of losing everything if there's a problem with this file.
An Outlook Profile can contain several PST files and it's common to have an additional one called archive.pst for storing older emails.
When Outlook operates with an Exchange server your email data is stored on the server and not in a local PST file however, to enable you to continue to work when not connected to Exchange, a very similar file will exist in that same location called
Outlook.OST (Offline Storage Table) which contains all your Outlook data, synchronised with the master copy on the Exchange server.
There are utility programs, such as EasyRecovery Professional from Ontrack, which will convert an OST file to a PST file.

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Push Email or Direct Push Technology

To be able to access your email on a mobile device is only half the story.
For full mobile functionality, new emails should arrive by themselves into your device and alert you to their presence.
The doorbell was invented to stop you having to go to your front door every half an hour to see if someone's waiting there for you.
Push Email means that you don't have to keep using your mobile device to check if you have any new messages waiting (Pull Email) as new messages deliver and announce themselves.
This requires that your mail-server can make contact with your mobile device whenever it wants to. The poor man's Push Email system uses text messages to alert you to a new email and tries to compress some of the email's content into the limited size of an SMS text message.
For serious Push Email, your mobile device needs a permanent link to the Internet using the 3G or GPRS component of mobile phone networks.
Luckily mobile data is charged by the amount of data exchanged and not the length of time connected. Even so, Push Email isn't cheap.
One device dominates the Push Email market: the Blackberry from Canadian company Research In Motion (RIM).
I've never met anyone who owned a Blackberry who wasn't delighted with the mobile email experience it provides.
RIM have also managed to hide all the technical details from the user which can often prove too difficult and cause them to give up when trying to setup email on other mobile devices.
If email is an important part of the way you do business and you don't want to be tied to the office then you've probably already got a Blackberry.
Microsoft have now enabled Push Email to work with their Exchange Server without the need for a 3rd party provider such as Blackberry.

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RPC-over-HTTP
(Remote Procedure Call over HyperText Transfer Protocol)

My least favourite acronym, now, thankfully, Microsoft have renamed it Outlook Anywhere.

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Sender Policy Framework - SPF

SPF is a method of identifying legitimate mail-servers so they can be differentiated from those sending spam and virus emails.
SPF requires a new type of DNS record for mail-servers which holds a list of email domains for which the mail-server is authorised to send emails.
If a mail-server is attempting to send an email from an email domain with an SPF record that lists that server  as an authorised sender then it must be genuine, if not it may be spam or contain a virus.
SPF is a proposed standard not yet widely adopted on the Internet.
One concern is that any genuine email being legitimately forwarded through other mail-servers would not comply as even if the originating mail-server has a valid SPF record, the forwarding one would not.
A SmartHost would need an SPF entry for all the email domains it was forwarding for.
We've made the appropriate SPF records for our SmartHost but we're not currently using SPF non-compliance in incoming emails as a reason to increase the email's Spam Index.
At the moment many DNS servers cannot store the required SPF text record.
DomainKeys is a similar anti-spam initiative.

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SmartHost

A SmartHost is a mail-server that other mail-servers use to deliver their outgoing email for them.

Why? Because the smart-host is considered to have a better success rate at delivering email than they have.

Due to the prevalence of spam and virus email, many mail-servers want to check the bona fides of the sending mail-server before they'll agree to accept email from it.
Important considerations are:-

Maintaining a SmartHost's trustworthiness is an ongoing task and so it's often easier for a company to have their mail-server just use a smart-host rather than try to establish their server as a trustworthy email sender.

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Smartphone

A Smartphone is a mobile phone incorporating some hand-held computer features.
They are usually only slightly larger than a standard mobile phone but can access the Internet to browse webpages and check email.
Smartphones usually come with a standard phone keyboard and standard-sized screen, without the touch-screen ability.
Smartphones can still synchronise with Exchange server and perform push email.
They are the smaller cousins of PDAs.

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SMTP - Simple Mail Transfer Protocol

The method used to exchange email between mail-servers on the Internet.
It is also the most common way for email programs such as Outlook Express to send emails to their local mail-server for delivery.

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SMTPS - Secure SMTP

The original SMTP standard has no built-in security and so the contents of emails are sent over the Internet as plain text - as are passwords if authentication is needed.
SMTPS is a variation of SMTP which uses SSL to create a strongly encrypted link between an email program on a PC and a mail-server or between 2 mail-servers.
At present the majority of mail-servers cannot accept SMTP email over an encrypted link and so standard SMTP has to be used.
Although Arrowmail allows and encourages the use of SMTPS, we also have no control of whether the recipient downloads the email you sent them over an encrypted link or in plain text. Therefore sending email to our server over an encrypted link does not guarantee that it will have end-to-end encryption between you and the recipient.
There are ways to ensure your email remains encrypted and unaltered between yours and the recipient PC but these are measures you take on each PC,  not on the mail-server and require that your recipients prepare for this in advance.
Our advice is to connect to our mail-servers using secure protocols if you can but if some problem prevents it, perhaps a firewall, then use standard protocols instead and don't worry about it.

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SPAM

Officially: Unsolicited Commercial Email.

More Generally: Any email that arrives in your Inbox which you don't want.
At present there is a battle between the senders of spam and those attempting to block it and so, like the flu virus, the nature of spam keeps evolving to evade the counter-measures.
The good guys will probably win in the end but it may take another 5 years before this happens.

Spam broadly consists of:-

To maintain the accuracy of our anti-spam system there are certain types of unwanted emails that we don't consider as spam:-

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Spam Index

This is a number between -100 and +100 that our spam filtering system assigns to every email that passes through it.
The Spam Index is arrived at by adding together the scores of several different spam classification methods.
The following table shows what actions are taken depending on an email's Spam Index:-

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Webmail

Webmail is where you use a web browser, such as Internet Explorer, to read, write and send emails instead of using a separate email program such as Outlook Express.
Hotmail is probably the most famous example of a webmail system.
The big advantage of webmail is that you should be able to use it to access your email when all other methods have failed. All you need is a computer with Internet access, no configuration or extra programs are required and, when you've finished, the computer you used won't have any of your email information left on it.
Webmail is server-based so that you see the same set of folders wherever you access it and there's no local data on your PC that needs to be backed up.

The disadvantages of Webmail are:-

We certainly allow webmail access for all the accounts on our mail-server but, when possible, you'll have a better email experience if you use a separate email program.

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White-List

A list of email addresses known to be genuine senders.
Incoming emails from white-list members automatically get 100 subtracted from their Spam Index which almost guarantees that they will be classified as non-spam.
A white-list is used to reduce the number or false positives and, when a false positive is found, the sender's address is often added to the white-list.

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VPN - Virtual Private Network

A VPN is a way of connecting a computer in a remote location to a private network by means of the Internet in such a way that resources on the private network can be accessed by the remote computer just as if it were a locally connected computer.
Encryption is used to ensure that, while data is passing over the VPN, it's kept secret from anyone who may be able to access the VPN data stream as it travels over the Internet.
Even with a Broadband connection, the rate at which data can be transferred across a VPN is around 50 times slower compared with what can be achieved by a locally connected computer.
VPNs are therefore not always the best solution for remote access to private networks.

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