Sendmail: Theory and Practice, Second Edition
A comprehensive guide to the nooks and crannies of Sendmail, the most-popular electronic mail utility for those using Unix-based servers.
TABLE OF CONTENTS Sendmail: Theory and Practice, Second Edition
Appendix F: Log Levels
Sendmail's logging facility is tiered such that each log message has a certain level and you can specify in sendmail.cf which levels you care about. The vast majority of sendmail.cf files in use have the log level set to 9 (i.e., OL9), which means that messages with log level 9 or lower will be generated, and messages with log level 10 or higher will not be generated. Using this appendix, you should be able to make an informed decision about your OL x setting, on the basis of the kinds of messages you think you need to see in your logs. It is common to boost the OL x value when working on a difficult mail problem.
As you will see, log levels 10 and higher are of interest mostly to someone who is debugging Sendmail; they are rarely used by the average Postmaster. If you set the log level to 0, no messages are logged. No Postmaster has ever done this and lived to tell about it. OL9 really is a reasonable default.
The levels are as follows: [1]
| 0 | Minimal logging. |
| 1 | Serious system failures and potential security problems. |
| 2 | Lost communications (network problems) and protocol failures. |
| 3 | Other serious failures, malformed addresses, transient forward/include errors, connection timeouts. |
| 4 | Minor failures, out of date alias databases, connection rejections via check_rulesets. |
| 5 | Message collection statistics. |
| 6 | Creation of error messages, VRFY and EXPN commands. |
| 7 | Delivery failures (host or user unknown,... |
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