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GrußNun die Sendmail FAQ schreibt folgendes:
Subject: Q4.17 -- How do I handle user names with upper-case characters?
Date: November 18, 1999
Updated: August 8, 2001
You really shouldn't, because upper case characters in user names are contrary to the Unix tradition. If you do, then e-mail addresses will be case sensitive, so that mail to <USER@your.host> will bounce instead of being delivered to <user@your.host>. As this is contrary to the expectations of many, it is not recommended.
But if you insist on doing so anyway, and you have version 8.10, put the following in your .mc file:
MODIFY_MAILER_FLAGS(`LOCAL', `+u')dnl
If you don't have 8.10, you will need to redefine the LOCAL_MAILER_FLAGS m4 variable, but the initial value varies from OS to OS, so this is yet another reason not to mess with this flag.
Another hack is the creation of aliases for Uppercase local users in the form:
# lowercase version to real one
uppercase: Uppercase
It will make sendmail deliver messages to uppercase local recipients in a case insensitive manner.