Inbound email being rejected
I have email user who is having trouble sending me email, half of them are being rejected. I have his email address in my contact list. It appears that the AT&T email servers are flagging it as span or bad links. How do I resolve?
----- The following addresses had permanent fatal errors -----
(reason: 554 [RL02] Message content not accepted for policy reasons; see https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpostmaster.yahooinc.com%2Ferror-codes&data=05%7C01%7C%7Ccf5fae1b0bb84356e0d108db54b271b7%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C638196897611763479%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=srmhAKiGVwnZaNNGz2meXWhvxvxpNAhakM6aWjY8AzQ%3D&reserved=0)