epostalias

Epostalias is the term used to describe an email alias, an alternate address that forwards incoming mail to one or more real mailbox accounts. An alias does not hold its own mailbox; it serves as a forwarding entry that redirects messages to other addresses.

How it works: when mail is sent to the alias address, the mail system consults the alias map and delivers the message to the configured destination recipient(s). The sender sees the alias address, but the recipient mailbox receives the message as if it were sent directly to it. Aliases can be single destination or can forward to multiple recipients.

Implementation varies by system. On traditional Unix-like servers, alias mappings are often stored in a file such as /etc/aliases and processed by a local delivery agent. Mail transfer agents like Postfix or Exim can use virtual alias maps, which are typically stored in databases or text files and may map domains and addresses to one or more destinations. In cloud and hosted environments, administrators commonly create aliases through admin consoles in services like Google Workspace or Microsoft 365, where an alias is assigned to an existing user mailbox.

Distinctions: an alias differs from a distribution list, which expands to multiple recipients, and from a mailbox forwarder that forwards messages to external addresses. A catch-all mailbox is a related concept but serves a different purpose by capturing messages sent to undefined addresses.

Administration considerations include keeping alias lists up to date, avoiding spoofing, and ensuring deliverability with proper SPF, DKIM, and DMARC configurations.