[IMGate] Retry on SAV

[Gerry Massat]

I just noticed that Sender Address Verification has a 3 hour wait before doing a 
second verification attempt. For example, Postfix logs:
'Sender address rejected: unverified address: conversation with 
smtp.tiscali.cz[213.235.135.72] timed out while sending MAIL FROM'
I've had several instances where an overzealous MTA (or more likely, virus) keeps 
retrying 2-3 times every 5 minutes.  What setting in main.cf would control that?