MIME support in V8 sendmail has been coupled to ESMTP and the BODY parameter for the MAIL command. The BODY parameter is passed through as is to the delivery agent. Two special parameters are internally recognized by sendmail. They tell sendmail that the message body is either 7bit or 8bitmime. 7bit forces the high bit off. 8bitmime causes sendmail to leave the high bit unchanged. Both override any setting of the SevenBitInput option (SevenBitInput).

When sendmail accepts a connection with another site for incoming mail, it has no way to determine from context whether it is dealing with MIME mail. To override any configured assumptions, you can use the -B command-line switch:

-B 7BIT
-B 8BITMIME

Case is unimportant (7BIT and 7bit both work). The 7bit causes the local sendmail to tell the remote sendmail (in ESMTP mode) that the message body should have the high bit stripped from every byte. Conversely, 8bitmime tells the remote sendmail to preserve the high bit of each byte.

The value given to this -B command line or received via the BODY parameter is stored in the ${bodytype} sendmail macro (${bodytype}).