The block editor does not provide much help with creating a hyperlink to an email address. To do this you have to do the following in the text editor:

Select the text to be used for the hyperlink, then the hyperlink icon. 

In the pop up box, type β€œmailto: β€œ (without the quotes), then type or paste the email address.

Click the β€œreturn” arrow to the right of the box.