MailboxAlert is an application that regularly checks whether your email accounts are filled up to their storage limit, which prevents you from receiving mails. MailboxAlert periodically polls your mailboxes and if one of your accounts is filled above its threshold it lets you know with alerts, on-screen notifications and a changed menubar icon. You can enter as many accounts as you want and freely define polling intervals and thresholds. MailboxAlert supports all standards-compliant IMAP email accounts with and without SSL encryption.
What's new in MailboxAlert
Note: Now requires OS X 10.10 or later
Added refresh-button to refresh information about all mailboxes
Fixed icon display when menubar has ben set to be 'dark' in the System Preferences