Whilst investigating an e-mail I received from a certain email@example.com I came across this list of other spammers that you can check against your own ‘dodgy’ mail.
Got a new registered member on another WordPress based website today and searched adol77dai51 with Google. Lots of people have been getting their first registration as member adol77dai51. Spam perhaps? Maybe, but seems benign moreover. All the same I will be removing him/it (adol77dai51) from my user registration list.