Email sent from an unknown Gmail account to my account dept. made to look like it was from me

Someone sent an email from a random Gmail account to my accounts dept at work and made the email look like it was from me (they included my email signiture and signed off with my name). They would have had to have seen one of my emails to do this as the signature has some unique styling. I've gone through my sent items and I haven't sent many external emails and those I have sent have gone to reputable people. …

account accounts email gmail name privacy random work