I have a windows server 2003 system set up with IIS/SMTP (no
POP/Exchange).

I have turned basic authentication on to implement some basic
username/password security. However some users trying to send email
through my server are having problems, specifically using the Eudora
mail client. Although they have "allow authentication" turned on in
their SMTP settings in the mail client, the IIS server returns "530
5.7.3 Client was not authenticated" for them. Users using thunderbird,
outlook express, etc. are not having any problems connecting.

I think this may be because of the SMTP authentication methods
supported by Eudora - the documentation says that "The preferred SMTP
authentication method is CRAM-MD5. If CRAM-MD5 is not available, LOGIN
or PLAIN will automatically be used."

Can anybody help?

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