Throwing hardware at a problem isn't the solution - the system should behave in a sane manner when down.
Note that the responder says that he sees this problem all the time with Exim/LDAP combinations like I use on this server. I’ve not had a real problem with Exim screwing up because of LDAP dying. LDAP is up most of the time. I do wish there was a way to have Exim queue the mail (or even freeze it) if the LDAP server goes kaput. But that isn’t where I have the most problems.
No, the most problems come from the mail filter that I use. It craps out on large messages. And I can’t blame anyone but myself since I wrote it.