I used to use Dropbox all the time, but with my Office 365 subscription I moved to to OneDrive about 4 months ago and haven't used Dropbox since. I just got an email from "email@example.com" telling me my dropbox was lonely and reminding me what it can do. All other emails I have ever received from Dropbox came from "firstname.lastname@example.org". Do they really monitor account activity that closely? This email seemed strange to me.