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What are different Email protocols?

When we speak about email accounts, there are multiple protocols which are involved. This can be extremely confusing if you are not aware of what protocols exist for emails. Also, each of this protocols performs slightly different functionality. The commonly used protocols are- IMAP, POP3, SMTP, and Exchange. These are few protocol types one would come across while accessing an email client. The protocol details can be accessed via the server settings based on the email client being used.


POP3 stands for Post Office 3 protocol. POP simply reaches out to the mail server and brings back the mail contents. This is a simple yet standardized way which allows users to access mailboxes and quickly download messages to their device.

With POP3, users can configure the server settings. This can be used to allow mail copies to be left on the server or move all emails without leaving any copy on the server. This is usually configurable in most cases. The biggest advantage of POP3 is the low dependency over the Internet. Users can download all emails and read them at leisure even if they are accessing this offline.

The way these emails are stored in local depends on the email client. For instance, Outlook utilizes .pst, while Thunderbird uses .mbox. This is a good option in case you choose to read emails offline. Apart from this, this helps you reduce the server space by storing messages locally.

The default ports for POP3 are:

  • Port 110 – This is the default non-encrypted port.
  • Port 995 – This is the default port for secure connections.


This stands for Internet Message Access Protocol. This again is a standard protocol for accessing emails and is a client/server protocol. Here the emails are received and held by the Internet server. Unlike POP, this does not move the emails. The biggest difference between POP3 and IMAP is the mail sync up. POP3 assumes that a user will be connected to a single device. However, IMAP is suitable for different devices simultaneously.

IMAP requires users to be constantly connected to the Internet. When a user accesses the mailbox, the user is actually connected to an external server. This is more beneficial when there are multiple users. IMAP can work over a relatively low internet connection since it only downloads email messages from the server when a user has requested to read a specific email.

The default ports for IMAP are:

  • Port 143 – This is the default non-encrypted port.
  • Port 993 – This is default port for secure connections.


This stands for Simple Mail Transfer Protocol. This is a standard protocol for sending emails over the Internet. This is a protocol which is used by a Mail Transfer Agent to deliver emails to a recipient’s email server. This is a protocol which defines mail sending and cannot be used for mail receiving.

SMTP is the most commonly used protocol for mail transfer between two servers. This requires no authentication to function, unlike POP3 and IMAP. Certain Internet Service Providers block the default port 25 of SMTP. In such cases, the mail server also provides an alternate secondary port.

The default port for SMTP are:

  • Port 25 – This is the default non-encrypted port.
  • Port 465/ 587 – This is default port for secure connections.


This is a commonly known protocol and stands for HyperText Transfer Protocol. This is not an email specific protocol. However, HTTP is used for email access using web-based emails. Hotmail or Gmail are examples of using HTTP as an email protocol. This is used to compose and retrieve emails from a web-based account.

The default port for HTTP are:

  • Port 80 – This is default non-encrypted port.
  • Port 443 – This is default port for secure connections.

Exchange Account (EAS – Exchange ActiveSync)

This is used by Exchange servers like Microsoft Exchange. This not only syncs mail but also syncs contacts, calendars, notes and everything in the outlook. The advantage is that users can have a synced copy of the calendar, contacts over multiple devices.

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