From "a" seller or from any seller?
Are they Offer emails or something else.
Go to your Account Settings > Communication Prefs > and click through the sections to uncheck what you don't want.
Edit/expand Buying activity - Offers to buyers, or Marketing Comms
https://commspreferences.ebay.com/commsprefs
There should also be an Unsubscribe link at the bottom of those emails - it takes you to this same page.
