How to ensure that the Jira Cloud API is pulling User email?

I am using Celigo Integrator to form a connection between Jira Cloud and our Netsuite account. I would like issue information to be pulled from Jira and into Netsuite, including the assignee. I would like the integrator to be able to look up the assignee in the destination (Netsuite) by searching the email of the user who is the assignee.
Due to changs in cloud the API does not automatically pull the user email and I am unsure how to ensure my API is retreiving that information for all users are assignees of issues.