Email alias

Last updated March 30, 2019

An email alias is simply a forwarding email address. The term alias expansion is sometimes used to indicate a specific mode of email forwarding, thereby implying a more generic meaning of the term email alias as an address that is forwarded in a simplistic fashion.^[1]

An email address identifies an email box to which email messages are delivered. A wide variety of formats were used in early email systems, but only a single format is used today, following the standards developed for Internet mail systems since the 1980s. This article uses the term email address to refer to the addr-spec defined in RFC 5322, not to the address that is commonly used; the difference is that an address may contain a display name, a comment, or both.

Email forwarding generically refers to the operation of re-sending an email message delivered to one email address to a possibly different email address(es).

Usage

Email aliases can be created on a mail server. The mail server simply forwards email messages addressed to an email alias on to another, the specified email address. An email alias may be used to create a simple replacement for a long or difficult-to-remember email address. It can also be used to create a generic email address such as webmaster@example.com and info@example.com.

example.com, example.net, example.org, and example.edu are second-level domain names reserved for documentation purposes and examples of the use of domain names.

On UNIX-like systems, email aliases may be placed into the file /etc/aliases and have the form:

local-alias-name: adifferentlocaluser, anotherlocaluser, an@external.user.example.com

Control issue

Messages forwarded through an email alias retain the original SMTP envelope sender and recipient. If the message is a blind carbon copy, the recipient can only tell whether the message was forwarded through the alias by examining the message headers. However, the standard does not mandate mentioning the envelope recipient in the headers. Therefore, recipients of a message may not be able to recover what email address has been used by the sender to eventually deliver the message to their mailbox.

Blind carbon copy allows the sender of a message to conceal the person entered in the Bcc: field from the other recipients. This concept originally applied to paper correspondence and now also applies to email.

Recipients who cannot trace what address the sender used are unable to ask the sender to stop sending, because the sender most likely will not be able to associate their current email address with the one used for sending. Even if users are able to learn the exact address used for sending, their mail client may not provide a convenient way to submit a reply using the latter as the sender address of the response. In other words, aliasing is not reversible. This is particularly relevant in opt-out situations where the sender does not provide a reliable mechanism in the body of the message. Typically, newsletters sent to undisclosed recipients can be sent submitting the body once along with a list of recipients, which is much less resource intensive than submitting a different body for each recipient. However, if VERP or BATV are being used (e.g. to prevent email backscatter), the electronic mailing list software will send individual messages to each recipient with a different SMTP FROM address.

The term opt-out refers to several methods by which individuals can avoid receiving unsolicited product or service information. This ability is usually associated with direct marketing campaigns such as, e-mail marketing, or direct mail. A list of those who have opted out is called a Robinson list.

A newsletter is a printed report containing news (information) of the activities of a business or an organization that is sent by mail regularly to all its members, customers, employees or people, who are interested in. Newsletters generally contain one main topic of interest to its recipients. A newsletter may be considered grey literature. E-newsletters are delivered electronically via e-mail and can be viewed as spamming if e-mail marketing is sent unsolicited.

Backscatter is incorrectly automated bounce messages sent by mail servers, typically as a side effect of incoming spam.

Abuse issue

The recipient's SMTP server sees only the forwarding system's IP address. In general it has no reason to trust the Received: headerfield generated by the forwarding system and does not know the originating system's IP address. Therefore, recipients cannot reliably distinguish spam to the alias address from spam generated on the forwarding system. When a recipient reports a message to his ISP as spam, the ISP credits that spam to the forwarding system. ISPs with low abuse thresholds may begin blocking email from the forwarding system.

An Internet Protocol address is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing.

Notes

↑ RFC 5321 defines alias expansion as opposed to the list expansion of mailing lists, noting that the replacement of the address to whom bounce messages are returned makes a key difference. An email alias is different from a contact group, or distribution list. According to Microsoft, a contact group is "a grouping of e-mail addresses collected under one name. A message sent to a contact group goes to all recipients listed in the group."

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[1] RFC 5321 defines alias expansion as opposed to the list expansion of mailing lists, noting that the replacement of the address to whom bounce messages are returned makes a key difference. An email alias is different from a contact group, or distribution list. According to Microsoft, a contact group is "a grouping of e-mail addresses collected under one name. A message sent to a contact group goes to all recipients listed in the group."