How to store emailid

I am making a static website and I’m also using an unsupported database (Cosmos DB) to store my user accounts so i believe I cannot use the built in login system.

In order to display users email id after login something like “Logged in as abc@gmail.com " or " Hi abc@gmail.com” i want to store email id of the user in a variable after user is logged in.

I have been reading about how email ids are considered as personal data (under GDPR) and should be encrypted / hashed.

So where should i store the email id to display it after log in ? Is it ok to store them in a global variable? What is a good and compliant practice?