Why are you apologizing?
I don't understand blog posts, emails and other messages that begin with an apology.
If you're sorry to interrupt me with that spam, don't send it.
If you know that yet another blog post on a topic that's not of interest to your readers will annoy them, don't post it.
If you're in HR and you know that no one in the office is going to read your office-wide spam about yet another inane meeting, don't bother us.
On the other hand, if it's important, if it needs to be said, if it benefits not just you but the recipient, then just send it. Instead of an apology, clearly label it so it's easy to ignore or discard. Even better, don't send everyone a message aimed at just a few people. It's easier than ever to focus on the people you need to focus on.
Just because it's more convenient for you to blast everyone in your address book doesn't mean it's smart.