Zoho Campaigns : Hide "Uncategorized lists" from contacts
When the signup form option is disabled in your mailing list, Zoho will consider it as a private list. Zoho won't display private list as an option to subscribe for the unassociated contacts when they click on Email Preference option. However when contacts exist in the particular uncategorized list click on the Email Preference option, Zoho will display the private list so that they can unsubscribe if they are not interested.

Private List will be displayed only to associated contacts to manage their existing preference and not for unassociated contacts to subscribe. User has to categorize them if not categorized we will display private list to associated contacts and public list to all contacts.
In the left menu bar, click on "Contacts" and go to "Manage Lists". Then, choose the mailing list where you want to deactivate your signup form and click on "setup".
Then deactivate the signup form concerned. Easy as abc!

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