Postfix versions 2.1 and earlier always rewrite message header
addresses, and append Postfix's own domain information to addresses
that Postfix considers incomplete. While rewriting message header
addresses is OK for mail with a local origin, it is undesirable
for remote mail:
- Message header address rewriting is frowned upon by mail standards,
- Appending Postfix's own domain produces incorrect results with
some incomplete addresses,
- Appending Postfix's own domain sometimes creates the appearance
that spam is sent by local users.
Postfix versions 2.2 give you the option to either not rewrite
message headers from remote SMTP clients at all, or to label
incomplete addresses in such message headers as invalid. Here is
how it works:
- Postfix always rewrites message headers from local SMTP clients
and from the Postfix sendmail command, and appends its own domain
to incomplete addresses. The
controls what SMTP clients Postfix considers local (by default,
only local network interface addresses).
- Postfix never rewrites message header addresses from remote
SMTP clients when the
remote_header_rewrite_domain parameter value
is empty (the default setting).
- Otherwise, Postfix rewrites message headers from remote SMTP
clients, and appends the
remote_header_rewrite_domain value to
incomplete addresses. This feature can be used to append a reserved
domain such as "domain.invalid", so that incomplete addresses cannot
be mistaken for local addresses.