Rather than using a teacher or student personal email account, consider a class email account. Put a student in charge of checking each day for a response. Waiting for Answering. In some cases you can anticipate how long the response may take. Some classes maintain a bulletin board in their classroom where they post a timeline and responses.
Younger children have trouble waiting, so it's a good idea to select a timely expert.
In some cases, students are waiting for a response for a project. Again, you might want to prepare students for the possibility that the expert might not respond. Send Followups and Thank you's. When you get a response, be sure to send a thank you. If you have followup questions, it's a good idea to send them immediately and include copies of prior emails to remind the expert about previous conversations.