All mail sending fields would use the same data source, so what you describe
is not plausible.
You have not provided any information. Provide enough detail for us to tell
what you're doing. Include the precise steps by which you are entering the
names, your data source, your Outlook version and whether you're using
autocompletion and/or autoresolution.

Signature
Russ Valentine
[MVP-Outlook]
> How can I prevent Outlook remembering old email addresses that I have
> changed
[quoted text clipped - 5 lines]
>
> Thanks in anticipation