IMAP accounts (unlike POP accounts) normally will allways receive email automatically to the inbox (in realtime) even if you set the option to not synchronize in mail client options as is the nature of IMAP.
However you can disable an IMAP inbox folder from receiving email in eM Client “by adding a specific parameter” to the diagnostic tab of the mail account.
So to disable an IMAP account inbox folder from receiving email, see @Gary post on the following thread.
https://forum.emclient.com/t/can-i-disable-mail-retrieve/86670/3