edm customer loyalty SPAM-free email Email Marketing email SMS gmail sender reputation subscribers tips edm design SMS marketing marketing send list unsubscribe CRM Autoresponders CTA brand preheader drip marketing mobile responsive sender identity Facebook bounce Segmentation personal email Effective subject lines eCRM signup form engagement rate survey Call To Action Tel SMS Global personalize service platform relation MMS content 社交媒體 垃圾郵件 email market 情感營銷，價值營銷 Gmaii DNS responsive-eDM SPF Christmas DKIM promotion. eDM marketing DMARC eCard eCRM，顧客關係管理 online shop direct mailing 2017 Email Marketing whatsapp LBS