{{Short description|Forwarding email address}}
An '''email alias''' is a email address used for forwarding.<ref>{{Cite web |title=Add or delete an alternate email address (email alias) {{!}} User management |url=https://knowledge.workspace.google.com/admin/users/add-or-delete-an-alternate-email-address-email-alias |access-date=2026-03-22 |website=Google Workspace Help |language=en}}</ref><ref>{{Cite web |title=Add or remove email aliases in Exchange Online |url=https://learn.microsoft.com/en-us/exchange/recipients-in-exchange-online/manage-user-mailboxes/add-or-remove-email-aliases |access-date=2026-03-22 |website=Microsoft Learn |language=en}}</ref>
== Term == 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.<ref>{{Cite RFC |rfc=5321 |title=Simple Mail Transfer Protocol (SMTP) |publisher=IETF |date=2008 |section=3.9}}</ref>
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."<ref>{{Cite web |title=Create a contact group or distribution list in Outlook for PC |url=https://support.microsoft.com/en-us/office/create-a-contact-group-or-distribution-list-in-outlook-for-pc-8c1c5419-1c14-4a40-bcfd-1f3ffb6f0a90 |access-date=2026-03-22 |website=Microsoft Support |language=en}}</ref>
== Usage == Email aliases can be created on a mail server that simply forwards email messages addressed to an email alias on to another, the specified email address.<ref>{{Cite web |title=Aura Help Center |url=https://help.aura.com/s/article/what-is-email-alias |access-date=2026-03-22 |website=help.aura.com}}</ref>
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.<ref>{{Cite book |title= |language=ISO 639-1. |trans-title=arabic}}</ref>
On UNIX-like systems, email aliases may be placed into the file /etc/aliases and have the form:<ref>{{Cite web |title=aliases(5) — Postfix local alias database format |url=https://www.postfix.org/aliases.5.html |access-date=2026-03-22 |website=Postfix documentation |language=en}}</ref>
:<code>local-alias-name: adifferentlocaluser, anotherlocaluser, an@external.user.example.com</code>
== Issues ==
=== Control === Messages forwarded through an email alias retain the original SMTP envelope sender and recipient.<ref>{{Cite RFC |rfc=5321 |title=Simple Mail Transfer Protocol (SMTP) |publisher=IETF |date=2008 |section=2.1}}</ref>
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.<ref>{{Cite RFC |rfc=5321 |title=Simple Mail Transfer Protocol (SMTP) |publisher=IETF |date=2008 |section=3.3}}</ref><ref>{{Cite RFC |rfc=5322 |title=Internet Message Format |publisher=IETF |date=2008 |section=3.6}}</ref>
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.
=== Abuse === 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.<ref>{{Cite RFC |rfc=5321 |title=Simple Mail Transfer Protocol (SMTP) |publisher=IETF |date=2008 |section=4.4}}</ref>
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.
== See also == * Email forwarding
== Notes == <references/>
{{DEFAULTSORT:E-Mail Alias}} Alias