OJS 3: Notification emails go to junk/spam mailbox

The current conversation on OJS 2.4.8-1 regarding SPF, DKIM, and DMARC will apply to 3.0 as well.

For the emails being sent to spam, look in the message headers to see what the status of SPF, DKIM, and DMARC is. It will look something like this:

Authentication-Results: spf=neutral (sender IP is 127.0.0.1)
 smtp.mailfrom=a.domain.tld; mydomain.tld; dkim=pass (signature was verified)
 header.d=a.domain.tld;mydomain.tld; dmarc=fail action=none
 header.from=domain.tld;domain.tld; dkim=pass (signature was verified)
 header.d=a.domain.tld;
Received-SPF: Neutral (mailserver: 127.0.0.1 is neither
 permitted nor denied by domain of a.domain.tld)