The easy way is to ensure that your email account uses the IMAP protocol, rather than POP. Then you set up your account on both machines (or on three, four, five ... ) and the email server will ensure that what you see on each machine is the same. There are countless guides about IMAP and POP on the internet. Here's one I found that you may find helpful -- I encourage you to read and learn more: https://askleo.com/what_is_imap_and_how_can_it_help_me_manage_my_email/