Mail Default Server Question

Hello!
I have a new problem, which is by no means critical, but can cause problems.
In our home we have two identical MacBook Pro computers, both using OS X 10.6.8 Our Apple Mail version is 4.6 (1085). We each have multiple accounts in Mail.

Usually, if I send a message from my business account, the recipient sees that it is from [email protected]. If I send from a personal account, the recipient sees it is from [email protected]. This is automatic.

On only one of the computers, the new message always defaults to one of the servers. For instance, no matter which account writes the message, the recipient sees it is from [email protected]. She can manually change it for each message, but if she forgets, the receiver sees the wrong sender- sometimes causing problems with replies.

I went into Mail Preferences and tried de-selecting "Use Only This Server" for all of the accounts. No Luck. I tried re-selecting it for all. No Luck. Finally, I tried every combination of selected & de-selected. Again, it always defaults to the one, specific server (thus 'Sent From' address.) Each server works & the connection doctor showed no problems.

It never used to do this. What do you all think went haywire?

Bonus Question: Why, with the same Mail version & OS, does my Mail program look so much different than the other computer? For example, "Get Mail" on mine is on the left, on Grace's it is near the center, where it was before 10.6.8.
Just curious.

Thanks for any help you can give on the server question. We are appreciative!
Paul & Grace

Talking To Myself

Hi Folks-
I hope this is not a breach of forum etiquette, but I'm answering one of my above questions so that if others have this problem they might stumble across it.

Where I went wrong was that the problem of outgoing mail having the wrong sender name & address wasn't anything to do with the selected server in Mail-Preferences-Accounts. I guess the server has nothing to do with the sender's name, just who shoots it across the planet.

The solution, my wife found, was to go to Mail-Preferences-Composing and tell Apple Mail to "Send New Messages From" and click the drop down arrow to discover (and then celebrate the discovery) "Account Of Selected Mailbox".

I guess I have to learn that with OS X, tasks are generally accomplished in the simplest way possible & to look for a simple answer.

Hope this helps someone along the way.
Paul