To prevent abuse, a recent update to disabled easily guessable secret words. Please update your Mail2Blogger secret word.
I've referred to the importance of the "secret word" some time ago - and apparently this year, a few blogs are being hit by the vulnerability.
If you are using Mail-to-Blogger for publishing - and especially if you enabled "Publish emails immediately" - this is a change which you need to make.
There is an organised attack technique, where blogs, owned by accounts with weak "passwords", are being used as spam hosts. In some cases, this results in splog detection, with the well known and hated in forum triage being required, to get the blog unlocked - then cleaned.
If you are inadvertently using an author account, instead of your owner account, you may have enabled Mail-to-Blogger, while trying to recover control of the blog. Whether accidentally or intentionally, your blog is now vulnerable.
If your blog uses Mail-to-Blogger (Settings - "Mobile and email" - "Posting using email"), and you have selected "Publish emails immediately", please change your Mail-to-Blogger password, to something not easily guessable - but reliable. If you don't need to post using email, select "Disabled".
Just please - do this before you have to post, following organised brute force hacking, in Blogger Help Forum: Something Is Broken
Please, help me! My blog is locked!!