So emails I get from discourse-mediawiki.wmflabs.org have an envelope sender of gmail.com (For VERP I guess. reply-to is also gmail so i guess all inbound mail is handled by gmail), but don't come from gmail. So they softfail SPF.
Example:
ARC-Authentication-Results: i=1; mx.google.com;
spf=softfail (google.com: domain of transitioning discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com does not designate 185.15.56.19 as permitted sender) smtp.mailfrom=discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com
Return-Path: <discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com>
Received: from mx-out02.wmflabs.org (instance-mx-out02.cloudinfra.wmflabs.org. [185.15.56.19])
by mx.google.com with ESMTPS id d135si16525277qke.176.2019.10.13.22.37.34
for <bawolff+wn@gmail.com>
(version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256);
Sun, 13 Oct 2019 22:37:34 -0700 (PDT)
Received-SPF: softfail (google.com: domain of transitioning discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com does not designate 185.15.56.19 as permitted sender) client-ip=185.15.56.19;
Authentication-Results: mx.google.com;
spf=softfail (google.com: domain of transitioning discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com does not designate 185.15.56.19 as permitted sender) smtp.mailfrom=discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com
Received: from discourse-mw.discourse.eqiad.wmflabs ([172.16.7.141]:59240 helo=localhost.localdomain) by mx-out02.wmflabs.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from <discourse.mediawiki+verp-59f5dae0f1abef8d6c6dbef152564edc@gmail.com>) id 1iJt30-0005Tt-N5 for bawolff+wn@gmail.com; Mon, 14 Oct 2019 05:37:34 +0000This isn't the worst thing in the world, as most spam filters greylist. But it isn't exactly ideal.