GDPR has come into effect, and with it, far-reaching implications for email marketers around the world. While the General Data Protection Regulation may technically only apply to European Union citizens, most have adopted its principles on a global level to ensure full compliance. When it comes to email marketing, this means a sender must have proof of consent for every address they include in their distribution. Didn’t keep your original opt-in records, or maybe used some not-so-white-hat tactics a long time ago? Your email list could have just gotten a lot smaller. Here’s how to rebuild your email list with opt-in advertising.