SendMimeErrors

Return MIME-format errors V8.1 and later

MIME is documented in RFC2045 through RFC2049.[418] MIME is a method of incorporating non-ASCII text (such as images and sounds) in mail messages.

When sendmail composes an error notification of failed (bounced) mail, this SendMimeErrors option tells sendmail to include MIME-format headers in that error notification. MIME format is required for DSN notification to work (the two go hand in hand). This option affects only returned (bounced) mail.

If the SendMimeErrors option is true and if sendmail is composing a returned mail message, the following two headers are added to the header portion of that message:

MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
        boundary=magic

The 1.0 version of the MIME-Version: header (MIME-Version: on page 1160) is hardcoded into V8 sendmail, so it cannot be changed. The Content-Type: is instead multipart/mixed if sendmail was compiled without DSN support (DSN on page 111). The magic of Content-Type: is a string that is used to separate the various parts of the message body. The string is formed from the queue ID, the time, and the hostname. For example:

Content-Type: multipart/report; report-type=delivery-status;
        boundary="dBPEYdx00413.946132480/your.host.domain"

Then sendmail prefixes the body of the returned message (if there is one), a line of notification, and this boundary:

This is a MIME-encapsulated message

--dBPEYdx00413.946132480/your.host.domain
           ← message body begins ...

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