Electronic Mail

Internet Mail Protocols
SMTP  - Simple Mail Transfer Protocol
ESMTP - Extensions to SMTP
POP   - Post Office Protocol
MIME  - Multipurpose Internet Mail Extensions
IMAP  - Internet Mail Access Protocol
Components of an Electronic Mail System

Mail Relaying Architecture

Example:  Relaying Electronic Mail

The way that it works is:

Timestamps and Message ID

Each time that an item is relayed by a MTA, a timestamp is inserted, showing:

The Message-Id is added by the first MTA to handle the message.

View an email message that has been routed through several MTA's

Mail Recipient Identifiers and Mail Exchangers

Internet mail recipients are identified by names following the general pattern:

	local-part@domain-name

For many years, the prevalent format for mail names was:

	user@hostname

	e.g.,  hstern@krock.nyc.psvrn.com

Today, far more convenient formats are used, such as:

	first-name.last-name@mail-domain-name

	e.g.,	mboldin@niagarac.on.ca
		michael.boldin@sympatico.ca
		mbboler@hotmail.com
		mikeboldin@hotmail.com
		aa441@freenet.hamilton.on.ca
		boldinm@freenet.hamilton.on.ca
		aa441@hwcn.org
		boldinm@hwcn.org
		mike@tsb.ca
		mike@email.tsb.ca
		Mike_Boldin@email.tsb.ca
		Michael_Boldin@fp.cibc.com
		boldinm@cibc.ca

These convenient formats work because of the Domain Naming System (DNS).

Format of MIME Messages

Encoding Schemes

7 bit Ordinary ASCII lines of text
quoted-printable Mostly ASCII; a few special characters
base64 Mapped to look like ordinary characters
8 bit A sequence of lines ending in <CR><LF>
binary True binary data
x-token-name Any experimental encoding (i.e., not part of the MIME standard); must be given a name starting with x

View a MIME-compliant email message

Go Back to the CTEC1330 Page