m1ks came about through a need for a quick simple short and snappy easy to remember email address, the first online one created. Even back then it was nonsense like
'you can't have the username Michael as it is already taken, you can have this alternative, michael 5341531534534215345343501322.0.053453453011501242002101204514001, would you like to accept, if yes, click this button' etc
On reflection it was probably a good thing as an unbelievable number of people misspell Michael as Micheal, the only ones in my experience who don't seem to are named thus or have a family member who is.
Mike was gone, as was Mike.S Mikes Mick.s Micks (I hate the name shortened Mick, my parents always called me Mike but running out of ideas...)
I tried Mik.s Miks and finally M1ks, it accepted that and as it's my main email I stuck with the same name for forums etc.
I get a good few misinterpretation of this too oddly, though not for email, usually on forums and Mk1s probably people thinking it Mk, (Mark) 1 - S?