BuySellAds works with many different companies like Firefox, HGTV, and Roku.
They connect email newsletters with top brands to make direct sales with their marketplace. You deal with the advertisers directly so you have a chance to see exactly what the ads look like.
As the publisher, it gives you financial control by allowing you to set the rates for your advertisement space. They also offer ad block recovery, where you can recapture your lost revenue due to ad blockers.