I don't know if this issue was resolved, but I came across a similar issue with my coworker's iPad Mini today. Whenever a message was forwarded from email #1, it would list email #1 as the reply-to address, but after sending it, email #2 is shown as the sender. So it looks like the email was sent from a different email account.
I fixed this by first making sure that all the SMTP servers were turned "on" for that email account (IMAP) and then modified the primary server's outgoing mail server information by:
- filling in the User Name with your full email address (email@email.com)
- filling in the Password with the password used for your email address
- selecting "Password" to use for Authentication
And then save this information.
There's something similar to this on the desktop Mail application, in Preferences:
- Under Accounts, select the email account you're having trouble with in the left panel.
- Select "Edit SMTP Server List..." under Outgoing Mail Server (SMTP).
- Select the server your email uses, and below it, click on Advanced.
- Fill in User Name and Password with your full email address and its corresponding password.
- And select "Password" to use for Authentication.
- Click OK to save this information.
These directions were written based on my OS X version, but you should find something similar.
Let me know if this works for you. Good luck!