I see this in my (not Exim) SMTP server logs. A friend's Exim system says it's going to send me a 7124 byte message, but the message it sends using BDAT is actually 6001 bytes. I got the message, it's fine, the 6001 bytes is right. This seems fairly consistent among Exim systems that send me mail. The 6489 in the next line includes the Received and Authentication-Results headers added locally.
It's hardly a crisis, but it seems strange. R's, John 2021-04-09 07:44:55.348285500 mailfront[57623]: HELO x.x.net 2021-04-09 07:44:55.403838500 mailfront[57623]: MAIL FROM:<d...@x.net> SIZE=7124 2021-04-09 07:44:55.645717500 mailfront[57623]: RCPT TO:<jo...@taugh.com> 2021-04-09 07:44:55.648413500 mailfront[57623]: 2.3.0 Got 6001 octets. 2021-04-09 07:44:56.890727500 mailfront[57623]: 2.6.0 Accepted message qp 57627 bytes 6489 2021-04-09 07:44:56.916122500 mailfront[57623]: bytes in: 6116 bytes out: 345 2021-04-09 07:44:56.917293500 tcpserver: end 57623 status 0 -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/