There are a few different types of blocklists that I am aware of. The major subscription lists would probably see the forged headers and not block the domain. However, those blocklists that use user votes (the user clicking the spam button) and volume based blocklists typically would block the domain name.

In addition, this can damage a reputation. An unknown number of internet users are getting spam stamped with the domain name in question, and the vast majority of these users don't know anything about forged headers.

__________________
The best way to learn anything, is to question everything.