indeed thats what i saw too.  and this is probably because my site sends out tens of hundreds of messages every time someone sneezes on the site.   and someone was cleaning their email, marked it as spam, and when a few did this, the machine probably learned and decided to mark my IP as spam...
the hosting co i go with has nearly 200,000 customers... this is not anything ive experienced before, they are extremely well managed.
so i need to get to the bottom of this, and it's not something that is being solved just yet, but you did indeed arrive at the same error I noticed.
right now, right now is time to eat dried tart red cherries, and drink coffee.  :D