Working in Information Technology for years, I have to giggle a little when I see what a normal user's perspective is on how networking and the Internet should operate.
Unfortunately, their perspective is not accurate. Not by a long shot. I've had many calls over the years wondering why certain things aren't behaving the way they feel it should. And most of those questions revolve around email.
Email is very dynamic and varies by magnitudes from company to company. One organization might run a single Exchange server sitting on the Internet sending and receiving every piece of it's corporate email. In this situation, it is reasonable to expect an email to take anywhere from one second to eight hours to deliver a message through it, depending on what else is happening on the internet.
Another company might have ten mail servers. And guess what... You should still expect that delays are going to occur from time to time.
Many people think that email is the same as instant messaging, and it's not!! When you use an instant messaging client, you log into a server. That server keeps track of who is where, then one of two things happens. If you are user "A" and you want to say something to user "B", your computer might connect directly to user "B" and send the message. If firewalls are involved, the message will be sent to the server and the server will make the arrangements to deliver the message. In either case, this happens extremely fast.
Emails do not work this way. I have 5 different mail servers at work. They each have a different function and some ensure redundancy and availability while others ensure speed for the user experience. Regardless, there are many points where a message could be delayed.
The biggest reason for a delay will be for virus and junk mail scanning. Some companies do this in-house while others offload this chore to a third party. In either case, there is a chance for delay. Many junk filters do all sorts of checks which might involve a Bayes database. This is simply an adaptive learning process where the filter learns good mail from bad. If that database is not responsive, the message might be delayed or halted entirely if the filtering software is configured that way.
Another big reason for delays will be Internet Service Provider issues. If an ISP is hosting email and something happens with the mail application, mail may no longer work. During this mail outage, it is very common for other things to work normally like regular web browsing and instant messaging.
Some email delays would be caused by what I will term an email "storm". It's not uncommon for a company to, all the sudden, take on thousands of junk messages per hour. The way that email servers work, they cannot service every single request. If you send an email during this period, your mail server will hold on to your message and continue to attempt deliveries for a specified period of time. When the receiving server becomes available, your message will be accepted. It is normal for these storms to last many hours at a time.
Many companies today conduct business through email. It should be known that emails are not "instant" and are really no different than sending faxes. Just because you hit the send button on a fax machine and the paper goes through, it does not necessarily mean that the recipient will immediately receive your transmission. The sending fax machine will hold onto the fax if the line on the other end is busy. The end fax machine could hold on to the job if the tray is out of paper, toner, etc. Emails work in a very similar manner and have literally dozens of reasons as to why they could be delayed for longer that the "instant" that many users assume.
Craig Deering
Network Engineer
Astro Shapes, Inc. -
Aluminum ExtrusionsWebsite -
http://www.astroshapes.com
