According to the RFCs hostnames may not be case-sensitive.  If an MTA
is not accepting upper-case hostnames it is not compliant, period.  This
is not a LISTSERV problem, it's a problem with the receiving MTA.

Nathan

On Tue, 31 Aug 1999 06:40:38 -0400 Karen Reznek said:
>I've found that this can be an error when the receiver will accept the
>address after the "@" only in lower case. I'm dealing with one of these
>now, @TALK21.COM, and I've tried sending identical messages to the
>subscriber with the only change being whether the address is in upper or
>lower case. The lower case ones get through without a problem, and the
>uppercase ones always bounce with the relay message. Because internet
>conventions specify that the portion of the address after the @ should
>not be case sensitive, this is an issue to take up with the bouncing
>ISP. Listserv stores addresses with the portion after the @ in upper
>case.
>
>J. R. Lankford wrote:
>> Hi, can anyone explain to me what the "we don't relay" errors mean
>> that show up in the daily monitoring report now and then.
>
>--
>Karen Reznek
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