Manage your subscriptions here, Notification settings are on the right side. If you don't see the On/Off toggle, try viewing the page in a desktop browser. There's also a button at the top of the page to disable all email notifications for channels you follow:
For email notifications for comments on your videos, replies to your comments, and tips & tricks, you can disable those here: https://rumble.com/account/profile
Please note, you may still get some notifications up to 72 hours after turning them off if they were already queued to be sent.