User IDs are used for a variety of purposes in email campaigns:
Segmentation: By linking a User ID to specific subscriber data, marketers can create targeted segments and tailor their email content accordingly. Personalization: User IDs allow for the insertion of personalized elements such as the recipient’s name, purchase history, or preferences into the email content. Tracking: Unique User IDs enable the tracking of individual user behavior, such as open rates, click-through rates, and conversion rates.