I've been trying to use the mail identities feature in 4.5.0 OS. I can create new identities, but I can only seem to change the identity's name field. The email address is a drop down list which is populated with only the account that I'm logged in as. I fail to see how this can be useful as typically when changing email identities, I want to masquerade completely as another person/email address without disclosing the account that I'm using to send out as.
Is there anything that I missed out here?