see the same issue with the inbox messages?
Note: Using both IMAP and POP simultaneously or POP across multiple devices can cause connection/mail synchronization error messages when trying to send, receive or access new email such as the following:
“The mail server denied access to your account because another mail client was using it.”
To avoid these errors we recommend using IMAP on all devices.
POP and IMAP are two different email protocols used to access your email account.