Need help setting the mail-host-address and user-mail-address

[dick]

As you can probably tell my my return address, I haven't
been able to set either my user mail address or my mail host address.

When I attempt to do so gnus beeps at me and I see:

"This option has been changed outside the customize buffer. (mismatch)"

The minibuffer informs me that the "Symbol's value as variable is void."

The "(mismatch)" and the minibuffer tell me I've missed something,
but I can't figure out what.