Ipad: how does mail decide what the "reply to" address is?

Question

I have a weird problem.  Any mail I send from my iPad has the "wrong" reply-to address.  That is, when I send email from one account, it applies a different account address in the "from" field.
Here is the problem (all addresses are fake)
I have two email accounts on my ipad:  [email protected],  [email protected]  I specify "[email protected]" as the Default Account in Mail, Contacts, Calendars
I also have an old account ([email protected]).  This account was my AppleID, etc but I want to get away from that account and move completely to gmail.  Again [email protected] is NOT registered (installed?  what is the term) on the iPad.
Now, I would expect that when I send email, that "[email protected]" would be the "From:" address and that this would also be the reply-to address.
Indeed, when I make a New Message, the "From:" field DOES have [email protected]  I can also tap the From: field and it gives my two choices: [email protected] and [email protected]  However, when it arrives at the recipient, it says "From [email protected]".
Here is the header in Thunderbird when I send a test email from iPad to [email protected] (when I receive it), the header is really strange (again, edited to obfuscate my email):
From: Joe Blow <[email protected]>
Mime-Version: 1.0 (1.0)
Reply-To: [email protected]
Date: Tue, 12 Feb 2013 13:57:10 -0600
Delivered-To: [email protected]
Message-ID: <-2305465076252779989@unknownmsgid>
Subject: test of return address
To: Joe Blow <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
Sent from my iPad
Now this is a strange header.  It is missing all kinds of fields, (such as "Received:, Retur Path, etc) but it is clear that the iPad sen the mail with incorrect From and Reply-To fields.  I dont even have [email protected] as an account on the iPad.
So the question is:  where did it get and how do I fix it?
Any takers?
BTW, this is with iOS 5.1 (why, because every time I try to update, it says "An error occurred".

Answer 1

You don´t have to insert your e-mail adress in this field, if you don´t want to have the e-mail back to some other adress (that is the only purpose of this setting - just like in Outlook)
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