The -d27.2 debugging switch causes each :include: and .forward filenames to be printed before each is opened for reading:

include(file)

The -d27.2 debugging switch also causes additional information to be printed for the alias loop check described earlier:

self_reference(addr)
        ... getpwnam(user)...found   if in passwd file 
        ... getpwnam(user)...failed  otherwise 

The -d27.2 debugging switch also causes sendmail to print a message every time it sleeps while waiting for the aliases database to be rebuilt:

aliaswait: sleeping for secs seconds

Also, when processing the ~/.forward file, sendmail might experience a temporary inability to read it (such as when an NFS server is down). In that case the -d27.2 debugging switch causes the following message to be printed:

forward: transient error on home

Here the message will be queued and tried again later.