It essentially means that the emailed quote cannot immediately be delivered, but it hasn’t been completely rejected by the receiving emails server.
This is sometimes called a soft bounce.
We will continue to try for 72 hours to deliver a deferred quote.
In most cases we see that the deferred emails are delivered in under 5 minutes.
The best place to check to see if a quote has been delivered after being deferred is under the email history section on the quote.