Some users report that mails sent through MW from yahoo accounts end up in the spam folder on gmail: https://ro.wikipedia.org/wiki/Wikipedia:Cafenea#Probleme_e-mail
I've tried to reproduce this, but I was unsuccessful. I do suspect it might have something to do with a change Yahoo did in April: http://onlinegroups.net/blog/2014/04/10/yahoo-dmarc-better-mailing-list-manager/
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