email sent from wrong address

How many email accounts do you have on your iPad? When you get ready to send one of these emails that you are experiencing a problem with, how are you starting this email? The default account for email is designed to send email to anyone when you are outside of the Mail app and/or using another app to generate the email. If you are in email, you would need to be in the default account to send with it, otherwise it would send with whichever mail account you happen to be in at the time. Also, if you create an email and see that the From address is not the account you wish to use, if you tap on that From address, it should give you the option to change the account you wish to use. I'm not sure I understand what you mean by resetting the emails to the preferred account does not reset the account the iPad chooses. Can you explain that?

Okay, so you have five email accounts listed in Mail. When you check Settings>Mail>Default Account, it lists an account that you no longer use?? Did you delete that account from your device? Now, you did not respond to my question about how you are creating the mail that is getting sent by the wrong account. The next thing to check, go to Settings>Mail>Accounts>Select the account that you are trying to send from, select the account again, then go to Outgoing Mail Server (SMTP) and tap that. It should list the primary SMTP server name, and below that is an area Other SMTP Servers. Is anything listed there?

Like I said in my response, the primary SMTP server is generally the one that matches the account that you are in. Without having your device in my hand to see your individual setup it is difficult to answer "why" questions.

Generally the Primary SMTP server is going to be the one that matches the particular account that you are in. I'm glad you are satisfied with your results.