What key issues must be addressed when sending real-time Welcome emails linked to "Email ID" in an external database?

When sending real-time Welcome emails linked to "Email ID" in an external database, addressing how Marketing Cloud and the database will sync up is essential. Effective synchronization ensures that user information is accurate and up to date in both systems. This includes understanding what data fields are necessary for proper integration, determining the frequency and method of updates (such as real-time or batch processes), and establishing clear protocols for handling data discrepancies.

Having a robust sync mechanism allows Marketing Cloud to pull the latest user information, enabling it to send timely and relevant communications like Welcome emails. Proper integration also helps mitigate issues related to data consistency and compliance, which are critical for successful marketing campaigns and customer engagement.

While considerations about the presence of "Email ID" in new users, choices for Subscriber Key, and custom preferences are indeed relevant in a broader context, ensuring a seamless connection and data flow between Marketing Cloud and the external database is foundational to enabling effective email marketing strategies.