Data portability is your ability to move data out of tools you use. Open platforms embrace the concept of data portability. Data portability lets you avoid vendor lock-in.
Conversely, data is very difficult to move out of closed platforms. This is a dark pattern to enforce lock-in.
Vendor lock-in is a situation where customers face the high cost of losing useful information if they choose to switch to a competing vendor.
Email is a service with high data portability. Many email services have tools that allow you to migrate from a competitor.