Subject: Re: sendmail: Is this a bug? "Unknown User" or is my wrong?
To: None <>
From: Martin J. Laubach <>
List: current-users
Date: 02/23/2002 18:13:10
| > I'm currently running NetBSD-1.5.2. Today, I just created a new user to be
| > used as a mail-list receiver - uClinux (Note the capital C!)
|  SMTP protocol and DNS are case insensitive, so you can use
|  uClinux@domain, UCLINUX@DOMAIN or uCLiNuX@dOmAiN as your list address.

  No. The host name and domain part are case insensitive, the user
part, however, is whatever the receiver wants. I remember being caught
by a similar problem, that is sendmail not working well with mixed case
aliases -- after talking to the sendmail maintainers, they put in a
warning to that regard in the docs.

  There are a couple of FAQ entries to that subject:

>  Q: I can't send mail to users whose accounts have upper case letters. 
>  A: First: Don't use uppercase letters...: man 5 passwd on a SunOS 4
>	machine: 
>      username       is the user's login name.   This  field  con-
>                     tains  no  uppercase characters, and must not
>                     be more than eight characters in length.
> If you really need it, set the flag 'u' for the local mailer. If you
> don't have sendmail 8.10 you need to change the flags: 
> define(`LOCAL_MAILER_FLAGS', `urmn9')
> sendmail 8.10 provides a better way to do this: 
> See the Sendmail Installation and Operation Guide: 
> u   Upper case should be preserved in user names for
>     this mailer.
> If you use procmail as local mailer, make sure you define
> NO_USER_TO_LOWERCASE_HACK (in config.h?). 


> 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 <> will bounce instead
> of being delivered to <>. 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: 
> 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.