> That's the one that our EPA member can't join.
>
> Actually, it's not because of the EPA's filters - it's because Yahoo automagically capitalizes his e-mail address for some furkin' weird reason.
>
> The US EPA does it's e-mail addresses in the following manner:
>
> last.first@epa.gov
>
> If I enter his e-mail addres as that, Yahoo groups calls it
>
> Last.First@epa.gov - and he can't send e-mails TO the group.
>
> Go figure.
> "He who fights with monsters might take care lest he thereby become a monster. And if you gaze for long into an abyss, the abyss gazes also into you." - Friedrich Nietzsche
EPA's not RFC compliant then.

The user and host portions of an email address are supposed to be case-insensitive. The reason is that there are some systems which lack upper (or more often lower) case support. The Yahoo / EPA thing is totally borked -- both systems are screwed up. But you should have him ping his postmaster.

Relevant RFCs are 822 and 2822, along with a few others.