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