MC1251200 — Microsoft Viva Engage | Email sender domain migration from @yammer.com to @engage.mail.microsoft

Microsoft Viva Engage email sender domains have migrated from @yammer.com to @engage.mail.microsoft (and @eu.engage.mail.microsoft for Europe) as of March 31, 2026. Organizations should update mail flow rules, security gateways, and integrations referencing the old domains. No admin action needed unless custom configurations exist.