Bookwhen sends some automatic emails to your bookers (which you can read about here) and each time a booker replies to one of these emails the reply is sent to an admin.
By default, the email address that replies are sent to is the main Account Owner (usually the email address that signed up for the account). If you would like to set a different admin to be the 'reply-to' email address you can do so in Account Details.
The current 'reply-to' email address is indicated in the list of admins:
To change the 'reply to' email address simply click on the settings icon next to the admin and then click set as reply-to email address. The admin you changed the setting for will now be marked as the 'reply-to email' and all future responses will be sent to this address.
Get in touch with the support team if you have any questions or need any assistance!