List owners may notify you that subscribers who are using Office 365 for their email are seeing "failed fraud detection" warnings in Outlook when opening mail that has passed through LISTSERV.  Unfortunately there is not a list-level fix for this problem.

A site-level workaround for this problem was published in a LISTSERV at Work tech tip in mid-2017.  Please click here for the tech tip.  Please be aware that this is only a workaround, because Microsoft has declined to create a scalable solution for mailing lists.  Microsoft has also published theoretical solutions for the problem in their blog, but only the two solutions we discuss in our tech tip actually work.