I'm trying to improve the mail delivery for an organisation I work with (no spam). We have been using our normal mail service's smtp server as a smarthost for delivery, but recently they have blocked the account because it was sending too much mail.
I have looked into and signed up for a SMTP relay service, but these are quite expensive. The reason I don't want to go with sending mail directly is that it's crucial all mail is delivered, and I don't want to be spending a lot of time checking logs to ensure our mail is getting through to everyone.
So I was wondering - Is it possible to setup postfix so that it will first try to send mail directly, and if this fails, then send the mail out through the smart host? This should allow us to send mail to everyone but without having to pay to send all the mail through the SMTP relay.