The OTRS service received a complaint from the Mail.Ru Group company (one of the largest IT companies in Russia, providing mail services in the mail.ru, list.ru, bk.ru and other domains) that spam has recently been sent from the wikimedia.org domain. This is not news, spam from this domain has been known for many years (e. g. T103123). Due to constant spam, from which WMF is not protected in any way, Mail.Ru servers also reject emails from projects to mailing lists, which makes it impossible to use emails from this provider in Wikimedia projects.
And by now, instead of solving the problems with DMARC, time and effort has been spent on banning the use of postal services that require correct policies: T137603.
It is necessary to understand whether there are currently any problems in order to use a more restrictive policy, and if there are no such, then go for it.