Tim Coote via Postfix-users wrote in <d7c84b22-180c-4e2f-bd0b-3bb5c7d29...@coote.org>: |Thanks very much for the detailed response. My original issue was why \ |dkim signatures were failing on some emails from email lists when arriving \ |at my Postfix based domain (postfix-3.4.10-1.fc30.x86_64 - I know it \ |needs updating: and that may be the only reasonable answer). I have \ |only seen this sort of issue from two sources. So I tried subscribing \ |to one of them with a gmail address and found the folded header differen\ |ce, which, if the lines were merged meant that dkim signature verification \ |worked (using dkimpy). (tbh, I thought I’d done very well at this \ |point as I’d spotted what had gone wrong for DKIM). | |That’s why I formed a hypothesis that (my) Postfix had changed this \ |long header - as you note this is < 998 stmp limit. I presume it’s \ |not directly involved now, as smtp_line_length_limit is the default (998) | |So, I tried creating an email using python and sending that to an account \ |in my domain - that had the same <cr><lf><space> inserted after the \ |‘,’ in the ‘List-Unsubscribe’ header. But if I use the python to send \ |to an account in gmail, the behaviour is different from the externally \ |sourced email as the 'List-Unsubscribe’, when observed with the gmail \ |client in a browser does have an extra <space>, but no <cr><lf>. | |I clearly need to do several more experiments to work out what is going \ |on. It’s non-trivial when you control so little of the whole chain.
Note that in practice only exim and the DKIM library it uses (from 2009) produce really standard-conforming results, all other implementations i have tested have some edge cases. For example, opendkim and rspamd (as of git) use (at least in pars, or always) the C function isspace(3) to normalize whitespace, which is not allowed according to the DKIM RFC. They all do it wrong. The most minimum and in practice very likely non-failing (or not at all) is dkimpy (which uses the python function trim(), but only as the very last step). My upcoming sign-only milter will only support relaxed/relaxed, but is hard-conforming, too. --steffen | |Der Kragenbaer, The moon bear, |der holt sich munter he cheerfully and one by one |einen nach dem anderen runter wa.ks himself off |(By Robert Gernhardt) _______________________________________________ Postfix-users mailing list -- postfix-users@postfix.org To unsubscribe send an email to postfix-users-le...@postfix.org
