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Everyone loves optimized accelerated email!

Email is by far the most widely used tool for communications, providing the capability to send widely distributed announcements and to share information and files. Devices use different protocols depending on whether the email is coming or going from the device. SMTP is used to send email over the Internet. POP3 and IMAP are common protocols for receiving email.  (MAPI, a Microsoft protocol for receiving email is discussed separately.)


SMTP stands for Simple Mail Transfer Protocol. SMTP defines a set of codes that control the transmission of email messages between servers. Most email clients use SMTP to send the email.

An email message consists of multiple parts: a sender, one or more recipients, a message body, and usually a title.  SMTP identifies each section so email servers know how to handle each component. SMTP also manages communications between servers. It defines how servers identify and authenticate themselves, how servers announce intended functions, and how they handle errors – such as invalid email addresses.

SMTP is simple to set up and very reliable. It dates to the 1970’s before such things as music files existed. ESMTP (Extended Simple Mail Transfer Protocol) was created to manage multimedia attachments and commonly used today.

POP3, Post Office Protocol

POP3 or Post Office Protocol 3 is a popular method of receiving email. POP3 servers receive and hold the email for recipients until they pick it up. It permits users to check email from any computer in the world. POP works by contacting the email server and downloading all new messages from it. Once the messages are downloaded, they are removed from the server. If a user decides to check their email from a different device, the messages that have been downloaded previously will not appear.

Because POP3 is a basic method of storing and retrieving email, it can work with virtually any email program (provided the email server is configured to host the protocol). Many popular email programs, including Microsoft Outlook and Eudora, come configured to work with POP3.

POP3 has become increasingly sophisticated so that it can be set to store email on the server for a certain period of time and to allow users to download their mail multiple times within that time frame. However, this method is not practical for the vast majority of email recipients which is why alternate email retrieval protocols such as IMAP have become common. Even so, POP3 remains extremely popular among most email service providers because of its simplicity and high rate of success.


While POP3 was the most popular type of email protocol in days gone past, Internet Message Access Protocol (IMAP) is fast becoming the email protocol of choice for most people.

IMAP allows users to access their email messages from anywhere with an Internet connection. When IMAP users read an email message, they aren’t actually downloading or storing it on their computer.  Instead, they are reading it off of the server. As a result, it’s possible to check email from multiple devices at different times without missing a message.

There are multiple advantages to using IMAP.

  • First, it allows access to email messages from anywhere, via as many different devices.
  • Second, it only downloads a message when the title is clicked on. As a result, users do not have to wait for all of their new messages to download from the server before they can read them.
  • Third, attachments are not automatically downloaded with IMAP. This feature allows users to check their messages more quickly and to have control over which attachments are opened.
  • Finally, IMAP can be used offline just like POP which means users get the benefits both protocols in one.

As the world becomes more mobile device oriented, IMAP is increasing in popularity. The proliferation of smartphones, laptops, tablets and other devices is driving demand for IMAP services. While POP will remain popular for handling email messaging between server and with people who only access their email via one or two devices and for people on slow Internet connections, IMAP will remain the protocol of choice for most end users of email.

Acceleration Systems employs a suite of technologies to maximize email performance. First is the improvement of TCP performance over the connection as described in TCP Optimization. Second, the cumulative effects of Acceleration Systems’ block level deduplication, in-stream compression, and multiple caching strategies greatly reduce the number of bytes of data actually transferred over a connection when sending or receiving email. These techniques reduce the impact on bandwidth and results in faster transmissions. These benefits translate to a more positive email experience for all users on the network.