To perform delivery, sendmail often has to set its uid to something other than root's. The logic behind that process is described in Section 12.2.2. The -d11.2 debugging switch tells sendmail to print the real and effective user-ids that it is running under during delivery:

openmailer: running as r/euid=real-user-id/effective-user-id

Also, the -d11.2 debugging switch causes sendmail to print any error response that might be produced by a delivery agent:

giveresponse: stat=status, e->e_message=what

Here, status is the number of the error that caused delivery to fail (or succeed if it is 0) as defined in <sysexits.h>. The what is either the error message produced by the delivery agent, or "<NULL>" if the delivery agent was silent.