What do lowest numbered MX record points to local host and remote host address is the local host mean?

Why does Exim say all relevant MX records point to non-existent hosts when MX records point to IP addresses?

How do I configure Exim to send all messages to a central server? I don't want to do any local deliveries at all on this host.

How do I configure Exim to send all non-local mail to a gateway host?

How can I arrange for mail on my local network to be delivered directly to the relevant hosts, but all other mail to be sent to my ISP's mail server? The local hosts are all DNS-registered and behave like normal Internet hosts.

How do I configure Exim to send all non-local mail to a central server if it cannot be immediately delivered by my host? I don't want to have queued mail waiting on my host.

The route_list setting ^foo$:^bar$ $domain in a manualroute router does not work.

I have a domain for which some local parts must be delivered locally, but the remainder are to be treated like any other remote addresses.

How can I configure Exim on a firewall machine so that if mail arrives addressed to a domain whose MX points to the firewall, it is forwarded to the internal mail server, without having to have a list of all the domains involved?

If a DNS lookup returns no MX records why doesn't Exim just bin the message?

When a DNS lookup for MX records fails to complete, why doesn't Exim send the messsage to the host defined by the A record?

Is it possible to use a conditional expression for the host item in a route_list for manualroute router? I tried the following, but it doesn't work:

route_list = * ${if match{$header_from:}{\N.*\.usa\.net$\N} \
             {<smarthost1>}{<smarthost2>}

I send all external mail to a smart host, but this means that bad addresses also get passed to the smart host. Can I avoid this?

I have a really annoying intermittent problem where attempts to mail to valid sites are rejected with unknown mail domain. This only happens a few times a day and there is no particular pattern to the sites it rejects. If I try to lookup the same domain a few minutes later then it is OK.

I'd like route all mail with addresses that can't be resolved (the DNS lookup times out) to a relay machine.

I would like to forward all incoming email for a particular domain to another host via SMTP. Whereabouts would I configure that?

What I'd like to do is have alternative smart hosts, where the one to be used is determined by which ISP I'm connected to.

Exim won't route to a host with no MX record.

I have some mails on my queues that are sticking around longer than the retry time indicates they should. They are all getting frozen because some remote admin has set their MX record to 127.0.0.1.

How can I arrange for all mail to user@some.domain to be forwarded to user@other.domain?

How can I tell an Exim router to use only IPv4 or only IPv6 addresses when it finds both types in the DNS?

How can I reroute all messages bound for 192.168.10.0 and 10.0.0.0 to a specific mail server?