I'm not fully sure to understand the need here. Is it a one shot event which is forcing you to stop sending emails (doing it technically outside PRPC probably), or is it something you will have to handle on your application more or less constantly ?
I don't know which version of PRPC you having, but in general, the SendCorr agent is calling the Data-Corr-Email.Send activity. I guess one option would be to customized this activity in order to stop the outgoing email, you will need to either re-queue it or send it to another workbasket to resend it later on.
You could have your agent use normal periodicity so for example it runs every 15 minutes (or once a day, whatever). Every time it runs, it can check whether it is now time to send the email, and skip the send if it is not time yet. /Eric