I know hotmail/outlook.com does something similar. Completely blocks (never shows in SPAM and the sender doesn't get a bounce-back either) for a lot of "verification" emails (ie, you create an account on some forum, it sends you an email verification link and you never get it). The one time I was able to get an admin (from the sending system) to look at the logs, it appeared that MS would reject/whack the connection if the email had "too many links/URL's" So I created a gmail account to get around that, but seems that Google is now doing something similar.

I know my Chase electronic statements periodically don't make it to Microsoft as I'm randomly getting snail mail from Chase saying they couldn't deliver to [email protected]