If you have already disabled the Important Tag in your IMAP account as @sunriseal posted above, and your are still getting the important tag on your Gmail Inbox emails (which is strange your still are), then go online to your Gmail “Settings / Filters and Blocked address’s” and create the following filter which also worked for me before eM Client had the option within the mail client.
Thankz @Jay_Ogram for this info originally.
