The -d8.7 debugging switch causes sendmail to print a yes or no response to each of the "trying" line printed by -8.5. Yes means that the host could successfully be fully canonicalized. A yes answer prints just this:

YES

If the host could not be canonicalized, a more complex answer is printed:

NO: errno=errornum, h_errno=herrornum

The errornum is the system error number (if any) from <errno.h>, and herrornum is the resolver-specific error from <netdb.h>, as shown in Table 16-7.