This issue has been bugging me for a while and I finally figured out the cause.

There's a bug in Microsoft Exchange Server 2000 which causes message parts with a Content Disposition of "inline" to still be sent as attachments. So, the message body becomes an attachment.

I've successfully worked around the issue. I used to use the Path attribute for the attachment, but now I do this... 

my $mailfile_data;
if ( ! open(MAILFILE, "$mailfile") ) {
    Log( "Unable to open $mailfile for email report." );
    return FAILURE;
}

{
    local $/;
    undef $/;
    $mailfile_data = <MAILFILE>;
}

close MAILFILE;

$email->attach(
    Type        => "text/html",
    Data        => $mailfile_data,
    Disposition => "inline",
);

[download]
    Microsoft Knowledge Base Article - 323482
    http://www.ietf.org/rfc/rfc1806.txt
    http://www.ietf.org/rfc/rfc2183.txt

Microsoft's Knowledge Base claims that "This behavior is in compliance with the Request For Comments (RFC) 2803 and 1806.", however using their own links to the RFC standards mentioned, I found that it is not...

The presence of the filename parameter does not force an implementation to write the entity to a separate file. It is perfectly acceptable for implementations to leave the entity as part of the normal mail stream unless the user requests otherwise. As a consequence, the parameter may be used on any MIME entity, even `inline' ones. These will not normally be written to files, but the parameter could be used to provide a filename if the receiving user should choose to write the part to a file. 
--
-- GhodMode

In reply to MIME::Lite & MS Exchange 2000 by GhodMode

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