I think this construct is explained/mentioned in several places in the documentation. Section 20 of chapter 44 is one of them: "An exclamation mark preceding a condition negates its result."
https://www.exim.org/exim-html-current/doc/html/spec_html/ch-access_control_lists.html#SECTcondmodproc You should read it as !(...) (despite the counter-intuitive spacing) And please allow me to bring to your attention this message I sent a couple of days ago: https://lists.exim.org/lurker/message/20200711.202132.cfd68318.en.html It contains the configurations for SPF/DKIM/DMARC that I created for Exim on CentOS 8. On 7/16/20 2:25 AM, Phillip Carroll via Exim-users wrote: > To the maintainers: > > Help needed with a small grammar explanation. > > At the moment I am interested in (at long last) making my exim.conf > somewhat aware of SPF/DKIM/DMARC in some regard, which has led me to > perusal of Chapter 58 of the exim 4.94 spec. > > Coming from a world of Context-Free Grammars in general, and Backus_Naur > in particular, I frequently find myself bewildered by exim's---shall we > say---"interesting" configuration grammar. Nevertheless, I usually > manage after an exhaustive search of the latest version of the exim spec > to make sense of any constructs I come across in examples. > > However, the DMARC example of 58.5 contains a construct that has me > totally stumped: > > warn !domains = +screwed_up_dmarc_records > > In an exhaustive search of the PDF version of the spec, I found exactly > 98 occurrences of the symbol "!". Exactly one of those 98 instances (the > line quoted above) contains "!domains". None of the other 97 instances > appear to satisfactorily explain how to interpret the construct in > question. > > Presumably the left side of the "=" is negated in some manner, but that > is about as much as I think I understand. The right side looks > sufficiently close (linguistically speaking) to "foobar" that I think I > have some glimmer of understanding of that. But, maybe not. > > A pointer to the specific section of the spec that explains the concept > I am missing would be sufficient. > > Phil -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/
