proposal of similar names when writing a new message

[michael]

hi,
when you write a new mail you have the nice feature that
you get a list of similar addresses.
this list is growing with every new address you use.
well, this is cool.
but when i close my outlook or reboot my pc the list is
empty again and outlook must learn them all again..

is this a normal "feature" or a misconfiguration or a
real "feature"?

where is this list saved??

michael