Editing Sender Policy Framework (section)

===FAIL and forwarding===
SPF breaks [[Email forwarding#Server-based forwarding|plain message forwarding]]. When a domain publishes an SPF FAIL policy, legitimate messages sent to receivers forwarding their mail to third parties may be rejected and/or bounced if all of the following occur:
# The forwarder does not rewrite the [[Return-Path]], unlike mailing lists.
# The next hop does not allowlist the forwarder.
# This hop checks SPF.
This is a necessary and obvious feature of SPF – checks ''behind'' the "border" [[Mail transfer agent|MTA]] ([[MX record|MX]]) of the receiver cannot work directly.

Publishers of SPF FAIL policies must accept the risk of their legitimate emails being rejected or bounced. They should test (e.g., with a SOFTFAIL policy) until they are satisfied with the results. See below for a list of alternatives to plain message forwarding.