error using multiple email addresses in IMAP account

Thanks for reading - any help, advice or direction you can offer is very much appreciated!

Here is my situation: I use a single IMAP account with several email addresses. If it's important to know, they are all set up as aliases, so I can receive mail in one single account at all of the addresses and can send email from any of the addresses through the same SMTP account.

This behaves radically differently in Mail (iPhone and iPad) under iOS 6 than it did in iOS 5, and I need the behavior I had in iOS 5.

I am seeking help in figuring out how to make iOS 6 Mail behave the way iOS 5 Mail did.

Here's how I set it up in iOS 5: I used the primary email address (also my login for the IMAP/SMTP account) to set up the account on the iPad. This all worked. Once it was set up, I went back to settings and added the other email addresses as a comma-separated list in the "email" field after the primary one.

Then, when I went to compose a message (from mail, or from any other app), the default "from" address was the primary e-mail address (the first one listed), and it allowed me to tap on the "from" field and select a different one.

This changed in iOS 6, like this:

I set up the account the same way as above. With just the primary e-mail address it was fine. But when I added the other addresses and saved it, it seemed to choose one address at random from the list as primary (not the first one, not the last one, not the one first or last alphabetically, just one in particular - and the same one each time I tried this). Then when I compose mail, it defaults to that alternate email as the "from".

So:

I need to have it default to the primary email address as the "from," I need to have all the alternate emails available to me to choose from, and I need to have it all set up as one account. I have tried to set up a second account on the iPad with all the alternate email addresses, but since the IMAP and SMTP logins are the same, the iPad won't let me.

Any ideas, suggestions, direction, solutions, etc. are very much appreciated!

Details: iPad 2nd gen. WiFi+3G, iOS 6