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24.7 Interrelating Options | 969
24.7.5 Connection Caching
Connection caching improves the performance of SMTP-transported mail. In processing
the queue or delivering to a long list of recipients, keeping a few SMTP connections
open (just in case another message is for one of those same sites) will
improve the speed of transfers. Caching is of greatest benefit on busy mail hub
machines but can benefit any machine that sends a great deal of network mail.
Table 24-10 lists the options that determine how connections will be cached.
Note that beginning with V8.13, the ConnectionCacheSize and ConnectionCache-
Timeout options now also affect delivery agents that use P=[LPC] for delivery.
24.7.6 Problem Solving
The sendmail program offers a few options that will help in locating and solving
some mail delivery problems. Table 24-11 lists the available options.
Other means to solve problems are described in Chapter 15 on page 530, which discusses
the -d debugging command-line switch, and in Chapter 14 (specifically ?§14.2
on page 512), which covers the -X traffic-logging command-line switch.
SuperSafe ?§24.9.117 on page 1096 PostMilter setting delays fsync() until
after all Milters have reviewed the message
(V8.13 and later).
Timeout (r) ?§24.9.119 on page 1097 Set timeouts.
Table 24-10. Options that determine connection caching
Option name ?§ Description
ConnectionCacheSize (k) ?§24.
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