The cloudflare offical support said https://support.cloudflare.com/hc/en-us/articles/200168876-My-email-or-mail-stopped-working-What-should-I-do- But traditionally mx record should not set as cname http://www.exchangepedia.com/blog/2006/12/should-mx-record-point-to-cname-records.html But cloudflare has a service called "cname Flattening" is it related for a reason to set cname as mx records? So should i set cloudflare's mx record as cname ?