What is POP, POP3, IMAP, SMTP and SSL?

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What is POP, POP3, IMAP, SMTP and SSL?

Email client program (such as Microsoft Outlook or Outlook Express, Mozilla Thunderbird or Apple Mail.app) needs to be configured to use either IMAP or POP3 and SMTP. 
You might also want to consider using SSL to secure the transmission of your emails. So what do they all mean?


When email started POP3 (Post Office Protocol) was the standard. When using POP3 your email client accesses the mail server and sends your username and password. Then, it checks to see if there are new messages on the server and starts downloading them to your email client. In most cases, your email client deletes the email off the server after downloading them, so you don’t keep old mail from taking up unnecessary space on the server. Sometimes, your client will leave the email on the server so you can access it from another email client on another computer or view it from Webmail, however it is better to use IMAP in order to sync your email account between multiple devices.


Using IMAP (Internet Message Access Protocol) is a little different. You still use an email client, but instead of downloading the email from the server like POP3, the email client reads the email directly off the server and displays it in your client. You can then delete it or leave it there for the next time you are checking email. This is the preferred protocol to use in order to sync your email account between multiple devices. 


SMTP (Simple Mail Transfer Protocol) is a method for sending mail from one computer to another.

You want to send an email to your friend Bob, who has an account at otherdomain.com. You already know that Bob’s email address is [email protected], so you send your message in your email program (or using webmail) and address it to [email protected] Your computer connects to the SMTP server and tells it to send to [email protected] The SMTP server looks at the address and says, “I don’t know who Bob is, but I think I can get this over to otherdomain.com”. The SMTP server then performs a series of steps to find out how to get the email to otherdomain.com. Once it knows, it will then connect to the other SMTP server who is responsible for all mail for otherdomain.com. When your SMTP server talks to the otherdomain.com’s SMTP server, they exchange a series of messages and ultimately, the otherdomain.com says “sure, I’ll take the message to Bob” or it will say something like “no, there’s no Bob here, why you return it back to the sender”.


SSL (Secure Sockets Layer) is a standard security technology for establishing an encrypted link between a server and a client—typically a web server (website) and a browser; or a mail server and a mail client (e.g., Outlook, Mac Mail etc).

SSL allows sensitive information such as credit card numbers, and login credentials to be transmitted securely. Normally, data sent between browsers and web servers is sent in plain text—leaving you vulnerable to eavesdropping. If an attacker is able to intercept the data being sent between a browser and a web server they can see and use that information.

More specifically, SSL is a security protocol. Protocols describe how algorithms should be used; in this case, the SSL protocol determines variables of the encryption for both the link and the data being transmitted.

SSL certificates

SSL certificates are needed to establish an encrypted connection and these certificates have a key pair: a public and a private key. These keys work together to establish an encrypted connection. The certificate also contains what is called the “subject,” which is the identity of the certificate/website owner.

A ‘normal’ website doesn’t generally require the use of SSL, however if your website contains a web store and/or if you are collecting and processing credit card payments you should purchase an SSL certificate to secure these transmissions.

SSL for your emails are available through a ‘shared SSL certificate’. You can use this without any charge and when you add your email account to your devices you may receive a warning that the identity of the certificate cannot be verified. This is because the email client would pick up the shared SSL certificate. If it states that it is called ‘*.sau.net.au’ it is safe to continue and save the certificate as this is the certificate for the shared web server. 


By | 2016-11-23T22:53:59+00:00 April 23rd, 2016|Comments Off on What is POP, POP3, IMAP, SMTP and SSL?

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