Temporary mail queue services?

[Mike Lyon <mike.lyon () gmail com>]

Hello All,

Does anyone know of a service that you can sign up for to add as a secondary
MX to act as a mail queue if your primary MX isn't available? I'm going to
be doing a mail migration and I need a service to point my MX record to that
isn't my mail provider. I'll spare the details as to why it needs to be
different provider.

Any insight would be greatly appreciated.

Thank You,
Mike