I use some simple LWP::Simple tests to verify that my hosted websites are still working whenever I restart Apache. For the mailrouting, I wrote me a (still unreleased) module that basically queries exim4 for the rule that applies to a target mail address:

for (<DATA>) {
    my ($address,$expected_rule) = split / /;
    my @output = `exim4 -bt $mailaddress`;
    my @routes_as = grep /R:/, @output;
    is $routes_as[0], $expected_rule, "$mailaddress routes as $expecte
+d_rule";
};
__DATA__
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