The -d27.3 debugging switch causes each path for a possible .forward file to be printed before it is tried:

forward: trying file

Here, file is each file in the path of files declared by the ForwardPath option (ForwardPath).

The -d27.3 debugging switch also causes sendmail to trace its wait for another alias rebuild to complete (Section 12.5.1). First sendmail prints the database type (such as hash) and filename for which it will wait:

aliaswait(dbtype:file)

If the database is not rebuildable (as would be the case with a network database type, such as nis, nis+, or hesiod), the -d27.3 debugging switch causes the following to be printed:

aliaswait: not rebuildable

If the file specified doesn't exist, the -d27.3 debugging switch prints:

aliaswait: no source file

The -d27.3 debugging switch also causes sendmail to print an error message if there was a read error while processing a :include: or .forward file:

include: read error: reason here