When replying to a mail from the "Sent" folder, the default account is used instead of the one used for sending the previous mail
Currently when having multiple mail addresses configured in evolution but only a single "Sent" folder (not sure if that part matters), replying to any mail in the "Sent" folder happens from the default mail address.
Ideally it would take the one that was used for sending that mail instead, in the end there was a reason for selecting that one instead of using the default one previously.