Case-sensitive email address issues

We have a firstname.lastname naming format for all our Lotus notes users. When someone sends an email to a user with a capital F in the firstname, e.g. Firstname.lastname, then this mails goes to my error box. Is there some setting in Lotus where I can tell my server that if there is a case sensitive error in the Lotus user email ID, then map it to that person's correct email ID?

There is nothing that specifies case sensitivity that I know of in Domino. In fact, the SMTP lookup specifically says it does a case insensitive lookup to the $users view. I can't think of anything that would cause your problem.