I've been trying everything I can think of to get an email-enabled
document library to accept attachments from a public folder. It
would be very helpful if I could at least get an error message so
I'd know where in the process it was failing, but I get nothing.

I've set up Exchange and SharePoint exactly as described in the
Products and Technologies Resource Kit - I chose the option to grant
the anonymous user read items permission for the public folder on
Exchange rather than adding the application pool account. I did this
because Exchange and SharePoint are on two separate domains - and
I'm thinking that may be part of the problem. However, we've been
playing around with the firewall, and the Exchange public folder can
be accessed from the SharePoint server. I also followed some
instructions I found on Google Groups to set up an alternate
Exchange virtual server to get around forms based authentication
issues, but that didn't work either.

Can anyone help? I'm not sure what to do next.