MAILER-DAEMON@yahoo.com undeliverable mail
My husband's emails from him@aol.com to me@me.com are being returned at undeliverable from MAILER-DAEMON@yahoo.com:
Sorry, we were unable to deliver your message to the following address.
<xxx@me.com>:
554: 5.7.1 [CS01] Message rejected due to local policy. Please visit https://support.apple.com/en-us/HT204137
How do we fix this? We are both using Mac Mail.
MacBook Pro 15″, macOS 10.15