Why Outlook 2007 always sends mails from wrong account with multiple accounts

I am using Outlook 2007 for handling all my email accounts. It is configured to handle all of them but to sent any email use only one of my company's email address. It is set to default for sent emails. But the problem now is that every time I send any email, it is sent via other than my office email address? Can any one explain me why Outlook 2007 always sends mails from wrong account with multiple accounts?

Is your Outlook configured properly? You can choose which e-mail account you want to send each piece of mail from as follows:

1. On the File menu, point to New, and then click Mail Message.
2. On the Accounts menu, click the account from which you would like to send your mail.

The account you have set as your default account appears first in the list.

Are your accounts having the similar aliases of one master account? Are you using the same username and password for each account? If this is true then I think your Outlook must be using the same account for sending your emails in spite of it is not the one that you have configured. Use some different names for your accounts and see what happens.

When you have configured your Outlook for multiple accounts, to send your message it uses the email account that you have configured as the default. This feature overcomes the reply or forwarded emails that the message was originally received on. You can also specify the account to use via the Accounts drop down item as said previously. However there are certain conditions where a different outgoing email account is used silently without users information if Outlook finds some difficulty with the default account.