mail problem: 550 5.1.1 User unknown

[j773303]

I've a problem with mail to user "Jeff".
mail Jeff < /etc/hosts , would got the failed message "550 5.1.1 User unknown".
I think the "Jeff" account is no problem.
If the user name contains capital letters, then mail wouldn't send correctly. Does anyone has the esperience about username contains capital letters and mail failed ? Thanks in advanced.

[VK2COT · Accepted solution]

Hello,

This is a very well documented issue. See FAQ for sendmail:

Subject: Q4.17 -- How do I handle user names
with upper-case characters?

Answer: 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:

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. But, it depends on the
sendmail version...

Cheers,

VK2COT

[j773303]

Hello expert,
The sendmail is 8.11.1
Can you make an example how to modify aliases? assume the user name is "Jeff".
Many thanks.