There are a couple of scenarios that can result in getting an email from a sender that was thought to be blocked. Advertising emails from many legitimate companies are often a nuisance and target for blocking. Companies will often use a 3rd party service to send these of emails. 3rd party services will usually send the emails from multiple addresses, so blocking one can still result in receiving a similar message from one of the alternate addresses. Similarly, many senders of spam email will spoof the display name while using random email addresses to send a message. It can appear that you are receiving email from the same sender based on the display name, but closer inspection will typically reveal that the actual sender address is not the same as what was blocked.