Some of my messages take about an hour. From looking at the headers in these cases, it looks like the delay is always before the message is received (i.e., accepted) by mail.python.org. This looks like greylisting.
Yes, greylisting is one of the anti-spam arrows in the wider on mail.python.org. However, once your email address has passed that threshold, new messages from the same address should float through without delay. If you have one such message and have the ability to save the entire original message and all headers to a file (i.e., not Outlook), you might want to send it to postmas...@python.org for one of the smart folks there to investigate. Skip -- https://mail.python.org/mailman/listinfo/python-list