edm customer loyalty SPAM-free email Email Marketing email SMS gmail sender reputation subscribers tips edm design SMS Marketing marketing send list unsubscribe CRM bounce Segmentation personal email Effective subject lines signup form engagement rate sender identity Call To Action survey eCRM CTA Autoresponders drip marketing preheader brand mobile responsive Facebook personalize DNS relation SPF content DKIM 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 Tel LBS 社交媒體