February 26, 2009

What Causes Delays in Email Delivery?

Email is one of the most handy tools available to both individuals and businesses a like. It provides nearly instantaneous communication with friends, family, colleagues, and even that friendly Nigerian E-mailPrince who said he wanted to give me a million dollars.

For the most part, when you send an email, within a few seconds, the recipient has it, but sometimes, that email that you really really need doesn't show up when you expect it, and you don't know why. To understand why emails get delayed, you have to understand how an email is sent from one person to another.

When an email is sent, it doesn't just go from your computer, to the recipients computer, it follows a path along the Internet, and along the way has several stops.

  1. An email is created on your computer using a email authoring tool like Outlook or by using a webmail service like Gmail.
  2. Once you click send,the message is sent to your mail server.
  3. Your mail server then looks at the email, determines where it needs to send it according to DNS records the recipient company has set up.
  4. Your mail server then sends the message to the place listed,
  5. Many times, the server listed isn't actually the recipients mail server, it is an intermediary server set up as a spam filter or an archive server.
  6. The receiving server then forwards the message off to the real mail server
  7. The recipient then connects to their mail server and grabs the message.

This process seems simple right? not exactly. The Internet really is a series of computers, connected via wires, fiber optics, and other computers. An email must travel long distances, and a break down at any step, or between any step can cause a delay.

Some of the most common causes for delays and failed delivery that I see are the following:

  1. User Error: It is very common for someone to mistype an email address. If you are missing an email, get in touch with the sender, and have them read you the email address they are sending to (don't ask "did you send it to youremailaddress as they will just assume they did)
  2. Spam Filters / Grey Lists / Black Lists: Spam filters are meant to block spam, but sometimes they are wrong and block a legit email, which means the recipient doesn't get it, check your junk mail folder, or ask your admin to check the spam filter if you are missing something.
  3. Internet Connectivity Problems: Sometimes things break, and broken things causes delays. A bad connection between your computer and mail server, your mail server and a DNS server, your mail server, and the recipients mail server(s), or the recipients mail server and the recipients computer can all cause delays in email delivery. Because of this, email servers have rules on the configured to retry message delivery several times before you ever get an error that says the message could not be delivered.

The bad part about most of these delays is that there is little you, or your IT department can do about it. People make mistakes, computers make mistakes, and things break. The good part is, at least now you have a better understanding of how email gets to you, and are more forging towards your IT guy a little slack when he says there is little he can do to find that missing email for you. In fact, most times, I cant even look into email delays until the email actually gets there and I can take a look at the message header to see where the email has been and when it got there. But Ill talk about that another time.

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