I sent an email to an intended recipient. But the name of an UNintended recipient was added-not by me!

Ive sent an email to an intended recipient. Fine! But on the address header of the email appears the name of a third party. She is not the intended recipient but nor is she on my Contcts List! So what is going on?

Hello Alastair,
I am unsure about parts of your described issue - is the actual recipient address changed? Or is it just a different display name?
What version of eM Client are you running and what mail account does this happen on?

Regards,
Olivia