Postfix does not resend to email hosts which greylist when my PostGrey is installed

Without Postgrey enabled on my server, sending email to other destination hosts using greylisting works normally.
If I enable Postgrey on my server though, it does not retry when the email is greylisted on the destination server. Instead, it returns an immediate error (450) to my email client (Thunderbird) and does not resend later.

The maillog shows:
Jul 30 22:02:40 mail postfix/smtpd[18607]: NOQUEUE: reject: RCPT from 24.102.201.189.res-cmts.t132.ptd.net[24.102.201.189]: 450 4.2.0 khufu@isp.net: Recipient address rejected: Greylisted for 60 seconds; from=sal@silverstone.com to=khufu@isp.net proto=ESMTP helo=<air.wgpeters.net>

There are no further entries in the maillog for this source and destination.

Server is Centos 7.2, Webmin GPL.

Are you authenticating with SASL? I’m pretty sure our default configuration does not greylist mail from authenticated sources.

Yes, SASL is on and working.