There have been a few bounces, with the error "500 Host server does not support 8bitmime". This seems to be related to the encoding of currency symbols for some reason. If anyone has an idea of what the problem is and how to correct it, please let me know.

Ah yes, a classic.

Normally caused by an MS Exchange Server hiding behind an IIS box running the SMTP relay that comes with Windows.

Some versions of Exchange do not support 8bitmime. The IIS SMTP relay does support 8bitmime.

A client that supports 8bitmime connects to the IIS box via SMTP, the IIS box advertises that it supports 8bitmime so the client uses it and the IIS box accepts it. The IIS box then relays the message to the Exchange box via SMTP and tries to use 8bitmime. The Exchange server says "I can't handle 8bitmime" and the message gets bounced.

So, you either need to stop your "client" (in this case probably your SMTP server) trying to use 8bitmime, or more properly get the remote server fixed.

Fortunately fixing the remote server is easy (for the admin at least) by disabling 8bitmime on the IIS relay:

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q262168