Mail only sending through one account
I use Mail to manage 3 email accounts. 1 is my Mac email, 2 & 3 are gmail accounts. All of a sudden no matter what I do, everytime I send an email it says it came from account #3. Under preferences and composing I have "Send new messages from:" set to "account of selected mailbox." But if I wanted to send an email from account #2 I would highlight that account, click on compose new message, even double check that account #2 was listed next to "from" and click send. But then that email goes out with account #3 listed as where it came from. And if somebody replies, it comes back in through account #3. Any thoughts of how to fix this? Thanks!
MacBook Pro, Mac OS X (10.7.5)