POP3 is used for the transmission of e-mails. It is the 3rd version of the Post Office Protocol. With a POP3-capable mail program you can fetch mails from a server. Depending on the settings, the mail messages are deleted on the server after retrieval and then only stored on your end device (PC, tablet, smartphone or similar). You practically take the mails from the mailbox on the incoming mail server, which temporarily stores them for you until you retrieve them, just like you retrieve a classic letter from your mailbox. The mail transfer protocol POP3, a so-called ASCII protocol, is described in detail in the internationally valid RFC 1939 rule and generally uses port 110 or, in the encrypted case, 995, which must be enabled in the firewall rules if necessary.
Historical development
The Post Office Protocol was first developed for Unix, but can now be used by almost all operating systems if an appropriate mail software is installed on it. POP3 has been in use since 1988 and is subject to continuous, mostly minor adjustments to current developments in computer and Internet technology. POP1 came into being as early as 1984 and was replaced by POP2 just one year later. POP4, which is supposed to support additional functions compared to POP3, has not yet been able to establish itself. Instead, POP3S now makes it possible to transmit encrypted user data. For simple and clearly listed mail retrieval, you will still be able to use POP3 or, in most current mail clients, the default POP3S anyway, via a secure SSL (or TSL) connection.
Mail retrieval process
Authentication is required after connecting to the server to retrieve the mail received on the server. The user name is stored in the mail program. The password can also be saved, but for security reasons a query should be agreed upon in the settings. Then the password will be requested. This login data is now transferred to the server. The server then starts the actual transmission of your emails, one after the other. When all mails listed on the server have been transferred, the server usually executes a delete command. Exception: You have set in your client program that the messages already received should be left on the server. However, this exception only works if your mail provider allows and maintains a special extension that does not actually belong to POP3. After retrieval, the connection between server and client is disconnected.
assets and drawbacks
One advantage is that you do not have to be permanently online, but only at the time of mail retrieval. However, there is no synchronization between several client devices, which is a disadvantage. So you do not automatically have the same current status of your e-mails from every end device. POP3 can practically only handle the processes list, fetch and delete mails. If you want more functionality, it is recommended to use a different mail protocol such as IMAP to choose. In the case of simple POP3, the user data is partly transmitted in plain text. POP3S is somewhat more secure.
Setting up POP3 in the mail program
Prerequisites for retrieving e-mails via POP3 are the correct settings in a client mail program. Depending on the operating system and the mail software, these can be more or less extensive. However, the basic functions are the same in all mail clients. First select POP3 as the transfer method to be used. You first need your mail address previously registered with the mail provider, your User names and the corresponding password. Furthermore, the name or the IP address of the incoming mail server is required. Most modern mail programs search for the responsible server themselves after entering the mail address. Otherwise you can find the required server name on the support pages of the mail provider. With some mail programs it is also possible to set up a new mail address via this program. As a counterpart to POP3, you still need the outgoing mail server, which can generally send your mails via SMTP (Simple Mail Transfer Protocol) or, more recently, frequently via ESMTP (Extended Simple Mail Transfer Protocol). Often providers use the same server as for outgoing mail. In any case, you will find the name of the responsible server at the same place as the name of the POP3 server. Most mail clients automatically set the required incoming and outgoing ports. If necessary, these are also listed on the support pages of the provider.
