mainsleaze definition, from Internet Connection, Inc.

1. Spam emitted by a reputable, mainstream company (as opposed to fly-by-night Viagra oeddlers and the like). Sometime this happens in honest ignorance, but the reputation danage can take years to live down.

2. Occasionally used for a big-time spammer, with its own fat pipe, their own mailservers, and a pink contract. Almost impossible to get shut down.