Here are a few of the more useful options you can set in the
Setting this option limits the size of message that Exim will accept.
Setting this option limits the amount of an incoming message that Exim will
return as part of a bounce message.
If the system load exceeds the value given for this option, all mail delivery
is suspended, though messages are still accepted.
This is the maximum number of simultaneous incoming SMTP calls Exim is prepared
This option controls the amount of material that is written to the log. There
are also some options with names beginning with log _ that
control the logging of specific information.