Chapter 6. Tune Performance
When sendmail
is installed with near-default
settings, it provides excellent email services for most machines. But
when installed to service high loads, high volumes, or high rates,
special tuning becomes a requirement.
What’s New with V8.13
There are a few new items in V8.13 that affect performance tuning. They are described in other chapters but referenced here. In this chapter, we augment some of the knowledge imparted in the third edition of the sendmail book.
The
RequiresDirfsync
option (Section 24.1.12 [V8.13]) turns off theREQUIRES_DIR_FSYNC
(3.4.47[3ed]) compile-time macro’s setting at runtime. Turning off directoryfsyncs
increases performance—but at (possibly) increased risk.The existing
SuperSafe
option (24.9.107[3ed]) now accepts a newPostMilter
setting that delaysfsync
( )ing thedf
file until after all Milters have reviewed the message. This improves performance when a great deal of email is rejected by Milters that review the message body.The
Timeout.queuereturn.dsn
(Section 24.1.15[V8.13]) andTimeout.queuewarn.dsn
(Section 24.1.16 [V8.13]) options have been added. Use them to lower bounce timeouts, and thereby to create less congested queues and increase performance.Some sites have developed delivery agents that receive messages using SMTP over standard input/output. Such delivery agents use the
P=[LPC]
equate (20.5.11[3ed]) to achieve this effect. Beginning with V8.13,sendmail
enables connection caching (24.7.5[3ed]) for such ...
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