Add username in newsletter to reset password


yet another support mail... Sorry about this but I'm stuck...

I need to send a welcome letter to about 1000 new users. I want them to set(reset) their password by them self.

In the e-mail I send them to http://mypage/wp-login.php?action=lostpassword where they can enter USERNAME or E-MAIL

If they use the preferred way, e-mail, they will get an error when using the link. See screenshot:

So I have 2 options, try to fix so they can use e-mail, hard way? Or in the newsletter write their username.

Is it possible to do that? {USER_NAME} is in fact the display name, right? Is there any other way to fix this?

All the best