View email account information in Mail on Mac
Use the Account Info window in Mail to view information about an email account. For example, you can check the maximum and available space on the account’s mail server, and delete messages from the mail server as needed.
In the Mail app on your Mac, in the Mail sidebar, Control-click a mailbox, then choose Get Account Info.
In the Account Info window, click the Account pop-up menu, then choose an account.
Click a tab to view details about the account.
Quota Limits or Messages on Server: Monitor the size of mailboxes and messages on the mail server. This information can help you manage your messages when you exceed your account storage limits. For example, for an IMAP account, you can determine which mailbox uses the most space, show the messages, then delete them.
Summary: View a summary of account settings, such as those related to mail servers and security.