Basic functions of e-mail system are given as follows:

Composition refers to the procedure of creating messages and the answers. Though any text editor can be used for the body of the message, the system itself can give support with addressing and the numerous header fields attached to each message.  For example, when answering the message, the e-mail system can extract the originator's address from incoming e- mail and automatically put in it into the proper place in the reply.

Transfer It refers to the moving messages from the originator to the recipient. In large part, this  requires  establishing  the  connection  to  the  destination  or  any  o9f the intermediate  machine, outputting the message, and releasing the connection. The e-mail system should perform this automatically, without bothering and disturbing the user.

Reporting:  It has to perform with telling the originator what happened to the message. Was it delivered or is still pending? Was it rejected or accepted by the person? Was it lost due to some reasons? Number of applications exists in which confirmation of delivery is significant and may even have legal significance (''Well, Your Honour, my e-mail system is not very much reliable, so I guess the electronic subpoena just got lost somewhere'').

Displaying incoming messages is required so the people can read their e-mail. Sometimes conversion is needed or a special viewer should be invoked, for instance, if the message is a PostScript file or the digitized voice. Easy conversions and formatting are sometimes attempted as well.

Disposition is the last step and concerns what the recipient does with message after receiving it. Possibilities contain throwing it away before reading, throwing it away after reading the content, saving it, etc. It must also be possible to retrieve and reread the saved messages, forward them, or process them in the other ways.

Additionally to these basic services, some of the e-mail systems, especially internal corporate ones, provide a variety of advanced features. Move or when they are away for some time,  they  may  desire  their  e-mail  forwarded,  so  the  system  must  be  able  to  do  this automatically.

Most systems permit users to create mailboxes to the store incoming e-mail. Commands are required to create and destroy mailboxes, check the contents of mailboxes, insert and delete messages from the mailboxes, and so on.

Corporate  managers  frequently  require  to  send  a  message  to  each  of  their  customers, subordinates, or suppliers. This gives rise to the idea of the mailing list, which is a list of e-mail addresses. When the message is sent to the mailing list, alike copies are delivered to everyone in the list.

Other advanced features are carbon copies, high-priority e-mail, secret (i.e., encrypted) e-mail, blind carbon copies, alternative recipients if the primary one is not presently available, and the ability for secretaries to read and reply their bosses' e-mail.