DMARC_NO_REWRITE

Platforms

All 16.5-2018a and following EXCEPT z/VM.

Abstract

A list of domains and subdomains which should never be rewritten by the DMARC address rewriting function.

Example

z/VM:

DMARC_NO_REWRITE = 'EXAMPLE.COM *.EXAMPLE.COM'

Unix:

DMARC_NO_REWRITE="EXAMPLE.COM *.EXAMPLE.COM"

export DMARC_NO_REWRITE

Windows:

DMARC_NO_REWRITE=EXAMPLE.COM *.EXAMPLE.COM

Details

Under normal circumstances, when receiving mail for a list from a user in a domain that has a DMARC record containing "p=reject" or "p=quarantine", LISTSERV will by default rewrite From: line addresses into a format that will appear to be coming from the LISTSERV server's own NODE= address. For instance, for a LISTSERV node known as LISTSERV.EXAMPLE.COM, mail coming from a user at yahoo.com (which has a restrictive DMARC policy) will be rewritten as something like

00000003f16b4808-dmarc-request@LISTSERV.EXAMPLE.COM

when their posting is sent out to the list. LISTSERV will keep a permanent record of that equivalency, so that future mail from that user will always be rewritten to that address, and so that replies to that address will always be forwarded to the user in question at yahoo.com. (Note however that the user's real address is always preserved in the list archives.)

Organizations which use DMARC "p=reject" or "p=quarantine" for their own domain, and where the outbound MTA used by LISTSERV (i.e., in its SMTP_FORWARD_n= settings) is authorized to send from the organization's domain, may use the DMARC_NO_REWRITE configuration variable to prevent posters' addresses in their own domain from being rewritten, as may be desirable for policy or branding reasons.

Important: This feature should not be used to simply disable DMARC rewriting altogether. To do so will likely result in a great deal of LISTSERV mail not being delivered to domains that have "p=reject" or "p=quarantine" set in their DMARC record. L-Soft will not be responsible for loss of mail due to the misuse of this feature.

Warning: If a list is configured with "Send= Editor", editor addresses in the domains defined in DMARC_NO_REWRITE always will be rewritten if the domain has DMARC "p=reject" or "p=quarantine", without regard to this global setting. To avoid this behavior, replace "Editor" in the Send= keyword setting with the actual addresses of the editor(s).

Note: DMARC rewriting is not available for z/VM because because there is no DNS query support in the z/VM version.

Default Value

Set to null string, that is, LISTSERV will perform a DMARC rewrite for any domain configured with "p=reject" or "p=quarantine" in its DMARC DNS record.