A catch-all address is one that, in the absence of a mailbox with that exact name, receives all mail for the domain in which it resides.
So, if the accounts <info@example.com> and <sales@example.com> and <*@example.com> exist, and mail comes in for <sales@example.com>, it goes to that mailbox.
Mail for <support@example.com> is handled by the <*@example.com> account. This may be a forward or even a mailbox.
To retrieve mail from a catch all mailbox, either use login '*@example.com' or plain 'example.com' or even 'whatever@example.com'.