Email – POP, IMAP, SMTP … What Does It All Mean?

Article (PSA-0017)
Submitted by: Billy Joe Long
Company: PSA Computer Services
Titled: Email – POP, IMAP, SMTP … What Does It All Mean?
Original release date: December 1, 2021

Almost all of us use Email on a daily basis, but most of us have little idea as to what is happening “under the hood” when we send or receive an Email. Like an automobile, not knowing how it works is not a really big deal … until something stops working! A little bit of knowledge about how the automobile works can save you time and money. The same is true about Email.

This article intends to give you basic information about how Email flows from a sender to a recipient and the most common protocols used to perform these functions.

Email works a lot like regular mail works. With regular mail you write a letter and put it in your mailbox with the flag up. This flag lets your post-delivery person know you have an outgoing letter. The postal delivery person will take your mail to the post office, where it will be sorted and routed to the next destination. Each time it is sorted and routed it should, theoretically, be getting closer to the intended recipient address. Once delivered and when the recipient next checks their mailbox – voila! – they get the letter you mailed to them!

With Email you write your message in your Email program and click the send button. If all works as expected, it is sent from your Email program to your Email providers mail server. Your Email providers server then routes the Email to the next appropriate destination, until it finally ends up at the intended mailbox. Once delivered the recipient can use their Email program to download the message from their providers server or they can view their Email on the server directly without removing it from the server.

Email uses different protocols to transport your Email from and to your Email account. They can be grouped into two types: “Incoming” & “Outgoing”. Before looking at the common protocols used today, let’s get a working definition of protocol. An Email protocol is a standard method of information exchange between email clients (programs such as Outlook or Thunderbird) and Email servers (usually hosted by your Email service provider). One type of protocol is used to send Email (SMTP protocol) and the other type of protocol is used to receive Email (POP3 or IMAP).

Knowing this allows you to determine some basic facts about any Email issues you are experiencing. For example, if I am having trouble sending Email, and my Internet service has been verified as working, then my problem may very well be related to my send protocol (SMTP protocol) settings. If I am having trouble receiving Email, and my Internet service is working, then my problem may be related to my receive protocol (POP3 or IMAP) settings. This is a gross oversimplification of the Email troubleshooting process and is intended for basic discussion purposes only.

One last point on email protocols. The receive protocol you use makes a big difference in the way you view and work with your Email. If you need to check your Email from more than one device (computer, laptop and phone) then you should use the IMAP protocol. If you only intend to check your Email on one device then you can use the POP3 protocol, although IMAP is still recommended – if available.

When you use IMAP, your Email program functions as a “Viewer” through which you can view your Email and directories located on your service providers server. Your Email remains on their server(s) and is available for viewing by many devices at the same time. With POP3, your Email program downloads your Email to your computer and removes the Email from your service providers server(s). If you were to attempt to check your Email from a different device now, you would not see any Email other than those that came in since the last time you checked. This can lead to a very complex and confusing Email environment.

If you have questions concerning your email services call PSA Computer Services at (707) 601-1408.