I want all mail to go to two SMTP servers and each server does everything it would do if there was only one SMTP in the first place.
In other words people get mail in two places and they are out of sync.
The scenario is we have Google Apps AND a custom app that uses sendgrid.com parse incoming email. The problem being solved is the app is not 100% reliable and as such we need All incoming email to go to both places.
I have no idea what I should be looking up as the above goes against all common sense and standard IT practises....