System Management Guide: Communications and Networks

Debugging sendmail

There are a large number of debug flags built into the sendmail command. Each debug flag has a number and level, where higher levels print more information. The convention is levels greater than nine print out so much information that they are used only for debugging a particular piece of code. Debug flags are set using the -d flag as shown in the following example:

debug-flag:     -d debug-list 
debug-list:     debug-flag[.debug-flag]* 
debug-flag:     debug-range[.debug-level] 
debug-range:    integer|integer-integer 
debug-level:    integer

-d12            Set flag 12 to level 1 
-d12.3          Set flag 12 to level 3 
-d3-17          Set flags 3 through 17 to level 1 
-d3-17.4        Set flags 3 through 17 to level 4

The available debug flags are:

-d0	General debugging.
-d1	Show send information.
-d2	End with finis( ).
-d3	Print the load average.
-d4	Enough disk space.
-d5	Show events.
-d6	Show failed mail.
-d7	The queue file name.
-d8	DNS name resolution.
-d9	Trace RFC1413 queries.
-d9.1	Make host name canonical.
-d10	Show recipient delivery.
-d11	Trace delivery.
-d12	Show mapping of relative host.
-d13	Show delivery.
-d14	Show header field commas.
-d15	Show network get request activity.
-d16	Outgoing connections.
-d17	List MX hosts.

Note: There are now almost 200 defined debug flags in sendmail.