Client host rejected: Connection rejected due to site policy
I'm trying to send email to someone at University of Cagliari in Italy. His email is firstname.lastname@example.org. Comcast is refusing to send the message, returning the perminant error message below.
I know that the address is good. My friend (not using Comcast) has no problem sending email to this person. I believe that Comcast has some sort of blacklist/whitelist that I can access to permit my email to go through; what is it?
To eliminate the false premise that the problem had something to do with my email client, the message rejected below was sent using Xfinity webmail.
................. perminant error message from Comcast follows
Date: Wed, 06 May 2020 18:51:21 +0000
Subject: Permanent Error