Mac Mail 'automatically' synching with a Hotmail account..?!

Hi folks,

I was surfing just now, and hit a 'contact us' button on a website, which automatically loaded my Mac's Mail software as the default application to send the mail (a thing I've seen happen before), and, lo and behold, my ex-bf's hotmail from about the last three years started to load up into it (inbox and sent)! We used to live together and he used to use my Mac a lot, but he isn't that tech-savvy and he wouldn't have knowingly synched his hotmail up with my machine - he must have unknowingly clicked on something quite fundamentally important/inappropriate... Anyway, as all this mail loaded up, I highlighted and deleted it; then it got to about the date we actually split up, I didn't want to see any more, and I just quit the application.

So I guess I have a few questions: how on earth did it happen in the first place; will my deleting loads of his messages on my Mail app be mirrored on his hotmail account globally; is there a way I can disassociate my Mail app from his hotmail (not that I use it, but the temptation to spy on his messages - destructive and pitiful as it is - will, I imagine, rear its ugly head in my weaker moments, and past experience dictates that ignorance is bliss).

Thanks....

 

...it's that simple? Must be what he did without realising it - easy to imagine him doing so

Thanks for the help!