I didn't click on any links in the email. Is it possible that my signing into Lastpass (my ID for Lastpass is the same Gmail address as it is for Live) my Live account is accessed if I'm doing so in IE)? It's just really strange. Well that's strange, since as far as I know I never did that- still, it says it's from my IP address and everything. However, once I turn off my PC and get to bed, I turn on my tablet to find an email from 'Microsoft account team' which has been sent to the Gmail address (a different one from the one I was checking above) that is my Windows Live ID and is also associated with it, saying there's 'unusual sign-in activity' (presumably on my Windows Live account). Well, I guess it had been a while since I last used Lastpass in IE because Lastpass asked me to enter my master password and I was able to proceed as usual.
So last night it occurred to me to check an old Gmail address that I really don't check often at all, and I went to gmail's site (using IE, although I normally use Firefox), typed in the address, and because I didn't remember the password, clicked the LastPass icon to have it auto-fill it in.