sharing photos from iphone photo app by email

Hi there,

The default mail app for my iphone is yahoo, but I use 4 different yahoo email addresses. When I share a photo from my iphone photo app using the email fxn, it does get sent through yahoo - but it shows up as being sent through one of the yahoo accounts that I do not want. I have one yahoo address that I control that is my husabnds name - and that one is the 'from' account when I send a photo. Can anyone help me figure out how to change this default, how to select which yahoo address is the primary? Thank you!